Select Git revision
array.js 53.45 KiB
// Copyright 2006 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Utilities for manipulating arrays.
*
*/
goog.provide('goog.array');
goog.provide('goog.array.ArrayLike');
goog.require('goog.asserts');
/**
* @define {boolean} NATIVE_ARRAY_PROTOTYPES indicates whether the code should
* rely on Array.prototype functions, if available.
*
* The Array.prototype functions can be defined by external libraries like
* Prototype and setting this flag to false forces closure to use its own
* goog.array implementation.
*
* If your javascript can be loaded by a third party site and you are wary about
* relying on the prototype functions, specify
* "--define goog.NATIVE_ARRAY_PROTOTYPES=false" to the JSCompiler.
*
* Setting goog.TRUSTED_SITE to false will automatically set
* NATIVE_ARRAY_PROTOTYPES to false.
*/
goog.define('goog.NATIVE_ARRAY_PROTOTYPES', goog.TRUSTED_SITE);
/**
* @typedef {Array|NodeList|Arguments|{length: number}}
*/
goog.array.ArrayLike;
/**
* Returns the last element in an array without removing it.
* @param {goog.array.ArrayLike} array The array.
* @return {*} Last item in array.
*/
goog.array.peek = function(array) {
return array[array.length - 1];
};
/**
* Reference to the original {@code Array.prototype}.
* @private
*/
goog.array.ARRAY_PROTOTYPE_ = Array.prototype;
// NOTE(arv): Since most of the array functions are generic it allows you to
// pass an array-like object. Strings have a length and are considered array-
// like. However, the 'in' operator does not work on strings so we cannot just// use the array path even if the browser supports indexing into strings. We
// therefore end up splitting the string.
/**
* Returns the index of the first element of an array with a specified
* value, or -1 if the element is not present in the array.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-indexof}
*
* @param {goog.array.ArrayLike} arr The array to be searched.
* @param {*} obj The object for which we are searching.
* @param {number=} opt_fromIndex The index at which to start the search. If
* omitted the search starts at index 0.
* @return {number} The index of the first matching array element.
*/
goog.array.indexOf = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.indexOf ?
function(arr, obj, opt_fromIndex) {
goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.indexOf.call(arr, obj, opt_fromIndex);
} :
function(arr, obj, opt_fromIndex) {
var fromIndex = opt_fromIndex == null ?
0 : (opt_fromIndex < 0 ?
Math.max(0, arr.length + opt_fromIndex) : opt_fromIndex);
if (goog.isString(arr)) {
// Array.prototype.indexOf uses === so only strings should be found.
if (!goog.isString(obj) || obj.length != 1) {
return -1;
}
return arr.indexOf(obj, fromIndex);
}
for (var i = fromIndex; i < arr.length; i++) {
if (i in arr && arr[i] === obj)
return i;
}
return -1;
};
/**
* Returns the index of the last element of an array with a specified value, or
* -1 if the element is not present in the array.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-lastindexof}
*
* @param {!Array.<T>|!goog.array.ArrayLike} arr The array to be searched.
* @param {T} obj The object for which we are searching.
* @param {?number=} opt_fromIndex The index at which to start the search. If
* omitted the search starts at the end of the array.
* @return {number} The index of the last matching array element.
* @template T
*/
goog.array.lastIndexOf = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.lastIndexOf ?
function(arr, obj, opt_fromIndex) {
goog.asserts.assert(arr.length != null);
// Firefox treats undefined and null as 0 in the fromIndex argument which
// leads it to always return -1
var fromIndex = opt_fromIndex == null ? arr.length - 1 : opt_fromIndex;
return goog.array.ARRAY_PROTOTYPE_.lastIndexOf.call(arr, obj, fromIndex);
} :
function(arr, obj, opt_fromIndex) {
var fromIndex = opt_fromIndex == null ? arr.length - 1 : opt_fromIndex;
if (fromIndex < 0) {
fromIndex = Math.max(0, arr.length + fromIndex);
}
if (goog.isString(arr)) {
// Array.prototype.lastIndexOf uses === so only strings should be found.
if (!goog.isString(obj) || obj.length != 1) {
return -1;
}
return arr.lastIndexOf(obj, fromIndex);
}
for (var i = fromIndex; i >= 0; i--) {
if (i in arr && arr[i] === obj)
return i;
}
return -1;
};
/**
* Calls a function for each element in an array. Skips holes in the array.
* See {@link http://tinyurl.com/developer-mozilla-org-array-foreach}
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array like object over
* which to iterate.
* @param {?function(this: S, T, number, ?): ?} f The function to call for every
* element. This function takes 3 arguments (the element, the index and the
* array). The return value is ignored.
* @param {S=} opt_obj The object to be used as the value of 'this' within f.
* @template T,S
*/
goog.array.forEach = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.forEach ?
function(arr, f, opt_obj) {
goog.asserts.assert(arr.length != null);
goog.array.ARRAY_PROTOTYPE_.forEach.call(arr, f, opt_obj);
} :
function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2) {
f.call(opt_obj, arr2[i], i, arr);
}
}
};
/**
* Calls a function for each element in an array, starting from the last
* element rather than the first.
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this: S, T, number, ?): ?} f The function to call for every
* element. This function
* takes 3 arguments (the element, the index and the array). The return
* value is ignored.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @template T,S
*/
goog.array.forEachRight = function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = l - 1; i >= 0; --i) {
if (i in arr2) {
f.call(opt_obj, arr2[i], i, arr); }
}
};
/**
* Calls a function for each element in an array, and if the function returns
* true adds the element to a new array.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-filter}
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?):boolean} f The function to call for
* every element. This function
* takes 3 arguments (the element, the index and the array) and must
* return a Boolean. If the return value is true the element is added to the
* result array. If it is false the element is not included.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {!Array} a new array in which only elements that passed the test are
* present.
* @template T,S
*/
goog.array.filter = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.filter ?
function(arr, f, opt_obj) {
goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.filter.call(arr, f, opt_obj);
} :
function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var res = [];
var resLength = 0;
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2) {
var val = arr2[i]; // in case f mutates arr2
if (f.call(opt_obj, val, i, arr)) {
res[resLength++] = val;
}
}
}
return res;
};
/**
* Calls a function for each element in an array and inserts the result into a
* new array.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-map}
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?):?} f The function to call for every
* element. This function
* takes 3 arguments (the element, the index and the array) and should
* return something. The result will be inserted into a new array.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {!Array} a new array with the results from f.
* @template T,S
*/
goog.array.map = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.map ?
function(arr, f, opt_obj) {
goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.map.call(arr, f, opt_obj);
} :
function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var res = new Array(l);
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2) {
res[i] = f.call(opt_obj, arr2[i], i, arr);
}
}
return res;
};
/**
* Passes every element of an array into a function and accumulates the result.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-reduce}
*
* For example:
* var a = [1, 2, 3, 4];
* goog.array.reduce(a, function(r, v, i, arr) {return r + v;}, 0);
* returns 10
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, R, T, number, ?) : R} f The function to call for
* every element. This function
* takes 4 arguments (the function's previous result or the initial value,
* the value of the current array element, the current array index, and the
* array itself)
* function(previousValue, currentValue, index, array).
* @param {?} val The initial value to pass into the function on the first call.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {R} Result of evaluating f repeatedly across the values of the array.
* @template T,S,R
*/
goog.array.reduce = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.reduce ?
function(arr, f, val, opt_obj) {
goog.asserts.assert(arr.length != null);
if (opt_obj) {
f = goog.bind(f, opt_obj);
}
return goog.array.ARRAY_PROTOTYPE_.reduce.call(arr, f, val);
} :
function(arr, f, val, opt_obj) {
var rval = val;
goog.array.forEach(arr, function(val, index) {
rval = f.call(opt_obj, rval, val, index, arr);
});
return rval;
};
/**
* Passes every element of an array into a function and accumulates the result,
* starting from the last element and working towards the first.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-reduceright}
*
* For example:
* var a = ['a', 'b', 'c'];
* goog.array.reduceRight(a, function(r, v, i, arr) {return r + v;}, '');
* returns 'cba'
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate. * @param {?function(this:S, R, T, number, ?) : R} f The function to call for
* every element. This function
* takes 4 arguments (the function's previous result or the initial value,
* the value of the current array element, the current array index, and the
* array itself)
* function(previousValue, currentValue, index, array).
* @param {?} val The initial value to pass into the function on the first call.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {R} Object returned as a result of evaluating f repeatedly across the
* values of the array.
* @template T,S,R
*/
goog.array.reduceRight = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.reduceRight ?
function(arr, f, val, opt_obj) {
goog.asserts.assert(arr.length != null);
if (opt_obj) {
f = goog.bind(f, opt_obj);
}
return goog.array.ARRAY_PROTOTYPE_.reduceRight.call(arr, f, val);
} :
function(arr, f, val, opt_obj) {
var rval = val;
goog.array.forEachRight(arr, function(val, index) {
rval = f.call(opt_obj, rval, val, index, arr);
});
return rval;
};
/**
* Calls f for each element of an array. If any call returns true, some()
* returns true (without checking the remaining elements). If all calls
* return false, some() returns false.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-some}
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call for
* for every element. This function takes 3 arguments (the element, the
* index and the array) and should return a boolean.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {boolean} true if any element passes the test.
* @template T,S
*/
goog.array.some = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.some ?
function(arr, f, opt_obj) {
goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.some.call(arr, f, opt_obj);
} :
function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
return true;
}
}
return false;
};
/**
* Call f for each element of an array. If all calls return true, every()
* returns true. If any call returns false, every() returns false and * does not continue to check the remaining elements.
*
* See {@link http://tinyurl.com/developer-mozilla-org-array-every}
*
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call for
* for every element. This function takes 3 arguments (the element, the
* index and the array) and should return a boolean.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within f.
* @return {boolean} false if any element fails the test.
* @template T,S
*/
goog.array.every = goog.NATIVE_ARRAY_PROTOTYPES &&
goog.array.ARRAY_PROTOTYPE_.every ?
function(arr, f, opt_obj) {
goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.every.call(arr, f, opt_obj);
} :
function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2 && !f.call(opt_obj, arr2[i], i, arr)) {
return false;
}
}
return true;
};
/**
* Counts the array elements that fulfill the predicate, i.e. for which the
* callback function returns true. Skips holes in the array.
*
* @param {!(Array.<T>|goog.array.ArrayLike)} arr Array or array like object
* over which to iterate.
* @param {function(this: S, T, number, ?): boolean} f The function to call for
* every element. Takes 3 arguments (the element, the index and the array).
* @param {S=} opt_obj The object to be used as the value of 'this' within f.
* @return {number} The number of the matching elements.
* @template T,S
*/
goog.array.count = function(arr, f, opt_obj) {
var count = 0;
goog.array.forEach(arr, function(element, index, arr) {
if (f.call(opt_obj, element, index, arr)) {
++count;
}
}, opt_obj);
return count;
};
/**
* Search an array for the first element that satisfies a given condition and
* return that element.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call
* for every element. This function takes 3 arguments (the element, the
* index and the array) and should return a boolean.
* @param {S=} opt_obj An optional "this" context for the function.
* @return {T} The first array element that passes the test, or null if no
* element is found.
* @template T,S
*/
goog.array.find = function(arr, f, opt_obj) { var i = goog.array.findIndex(arr, f, opt_obj);
return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
};
/**
* Search an array for the first element that satisfies a given condition and
* return its index.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call for
* every element. This function
* takes 3 arguments (the element, the index and the array) and should
* return a boolean.
* @param {S=} opt_obj An optional "this" context for the function.
* @return {number} The index of the first array element that passes the test,
* or -1 if no element is found.
* @template T,S
*/
goog.array.findIndex = function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = 0; i < l; i++) {
if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) {
return i;
}
}
return -1;
};
/**
* Search an array (in reverse order) for the last element that satisfies a
* given condition and return that element.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call
* for every element. This function
* takes 3 arguments (the element, the index and the array) and should
* return a boolean.
* @param {S=} opt_obj An optional "this" context for the function.
* @return {T} The last array element that passes the test, or null if no
* element is found.
* @template T,S
*/
goog.array.findRight = function(arr, f, opt_obj) {
var i = goog.array.findIndexRight(arr, f, opt_obj);
return i < 0 ? null : goog.isString(arr) ? arr.charAt(i) : arr[i];
};
/**
* Search an array (in reverse order) for the last element that satisfies a
* given condition and return its index.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call
* for every element. This function
* takes 3 arguments (the element, the index and the array) and should
* return a boolean.
* @param {Object=} opt_obj An optional "this" context for the function.
* @return {number} The index of the last array element that passes the test,
* or -1 if no element is found.
* @template T,S
*/
goog.array.findIndexRight = function(arr, f, opt_obj) {
var l = arr.length; // must be fixed during loop... see docs
var arr2 = goog.isString(arr) ? arr.split('') : arr;
for (var i = l - 1; i >= 0; i--) {
if (i in arr2 && f.call(opt_obj, arr2[i], i, arr)) { return i;
}
}
return -1;
};
/**
* Whether the array contains the given object.
* @param {goog.array.ArrayLike} arr The array to test for the presence of the
* element.
* @param {*} obj The object for which to test.
* @return {boolean} true if obj is present.
*/
goog.array.contains = function(arr, obj) {
return goog.array.indexOf(arr, obj) >= 0;
};
/**
* Whether the array is empty.
* @param {goog.array.ArrayLike} arr The array to test.
* @return {boolean} true if empty.
*/
goog.array.isEmpty = function(arr) {
return arr.length == 0;
};
/**
* Clears the array.
* @param {goog.array.ArrayLike} arr Array or array like object to clear.
*/
goog.array.clear = function(arr) {
// For non real arrays we don't have the magic length so we delete the
// indices.
if (!goog.isArray(arr)) {
for (var i = arr.length - 1; i >= 0; i--) {
delete arr[i];
}
}
arr.length = 0;
};
/**
* Pushes an item into an array, if it's not already in the array.
* @param {Array.<T>} arr Array into which to insert the item.
* @param {T} obj Value to add.
* @template T
*/
goog.array.insert = function(arr, obj) {
if (!goog.array.contains(arr, obj)) {
arr.push(obj);
}
};
/**
* Inserts an object at the given index of the array.
* @param {goog.array.ArrayLike} arr The array to modify.
* @param {*} obj The object to insert.
* @param {number=} opt_i The index at which to insert the object. If omitted,
* treated as 0. A negative index is counted from the end of the array.
*/
goog.array.insertAt = function(arr, obj, opt_i) {
goog.array.splice(arr, opt_i, 0, obj);
};
/**
* Inserts at the given index of the array, all elements of another array.
* @param {goog.array.ArrayLike} arr The array to modify.
* @param {goog.array.ArrayLike} elementsToAdd The array of elements to add.
* @param {number=} opt_i The index at which to insert the object. If omitted,
* treated as 0. A negative index is counted from the end of the array.
*/
goog.array.insertArrayAt = function(arr, elementsToAdd, opt_i) {
goog.partial(goog.array.splice, arr, opt_i, 0).apply(null, elementsToAdd);
};
/**
* Inserts an object into an array before a specified object.
* @param {Array.<T>} arr The array to modify.
* @param {T} obj The object to insert.
* @param {T=} opt_obj2 The object before which obj should be inserted. If obj2
* is omitted or not found, obj is inserted at the end of the array.
* @template T
*/
goog.array.insertBefore = function(arr, obj, opt_obj2) {
var i;
if (arguments.length == 2 || (i = goog.array.indexOf(arr, opt_obj2)) < 0) {
arr.push(obj);
} else {
goog.array.insertAt(arr, obj, i);
}
};
/**
* Removes the first occurrence of a particular value from an array.
* @param {goog.array.ArrayLike} arr Array from which to remove value.
* @param {*} obj Object to remove.
* @return {boolean} True if an element was removed.
*/
goog.array.remove = function(arr, obj) {
var i = goog.array.indexOf(arr, obj);
var rv;
if ((rv = i >= 0)) {
goog.array.removeAt(arr, i);
}
return rv;
};
/**
* Removes from an array the element at index i
* @param {goog.array.ArrayLike} arr Array or array like object from which to
* remove value.
* @param {number} i The index to remove.
* @return {boolean} True if an element was removed.
*/
goog.array.removeAt = function(arr, i) {
goog.asserts.assert(arr.length != null);
// use generic form of splice
// splice returns the removed items and if successful the length of that
// will be 1
return goog.array.ARRAY_PROTOTYPE_.splice.call(arr, i, 1).length == 1;
};
/**
* Removes the first value that satisfies the given condition.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array
* like object over which to iterate.
* @param {?function(this:S, T, number, ?) : boolean} f The function to call
* for every element. This function
* takes 3 arguments (the element, the index and the array) and should * return a boolean.
* @param {S=} opt_obj An optional "this" context for the function.
* @return {boolean} True if an element was removed.
* @template T,S
*/
goog.array.removeIf = function(arr, f, opt_obj) {
var i = goog.array.findIndex(arr, f, opt_obj);
if (i >= 0) {
goog.array.removeAt(arr, i);
return true;
}
return false;
};
/**
* Returns a new array that is the result of joining the arguments. If arrays
* are passed then their items are added, however, if non-arrays are passed they
* will be added to the return array as is.
*
* Note that ArrayLike objects will be added as is, rather than having their
* items added.
*
* goog.array.concat([1, 2], [3, 4]) -> [1, 2, 3, 4]
* goog.array.concat(0, [1, 2]) -> [0, 1, 2]
* goog.array.concat([1, 2], null) -> [1, 2, null]
*
* There is bug in all current versions of IE (6, 7 and 8) where arrays created
* in an iframe become corrupted soon (not immediately) after the iframe is
* destroyed. This is common if loading data via goog.net.IframeIo, for example.
* This corruption only affects the concat method which will start throwing
* Catastrophic Errors (#-2147418113).
*
* See http://endoflow.com/scratch/corrupted-arrays.html for a test case.
*
* Internally goog.array should use this, so that all methods will continue to
* work on these broken array objects.
*
* @param {...*} var_args Items to concatenate. Arrays will have each item
* added, while primitives and objects will be added as is.
* @return {!Array} The new resultant array.
*/
goog.array.concat = function(var_args) {
return goog.array.ARRAY_PROTOTYPE_.concat.apply(
goog.array.ARRAY_PROTOTYPE_, arguments);
};
/**
* Converts an object to an array.
* @param {goog.array.ArrayLike} object The object to convert to an array.
* @return {!Array} The object converted into an array. If object has a
* length property, every property indexed with a non-negative number
* less than length will be included in the result. If object does not
* have a length property, an empty array will be returned.
*/
goog.array.toArray = function(object) {
var length = object.length;
// If length is not a number the following it false. This case is kept for
// backwards compatibility since there are callers that pass objects that are
// not array like.
if (length > 0) {
var rv = new Array(length);
for (var i = 0; i < length; i++) {
rv[i] = object[i];
}
return rv;
}
return [];};
/**
* Does a shallow copy of an array.
* @param {goog.array.ArrayLike} arr Array or array-like object to clone.
* @return {!Array} Clone of the input array.
*/
goog.array.clone = goog.array.toArray;
/**
* Extends an array with another array, element, or "array like" object.
* This function operates 'in-place', it does not create a new Array.
*
* Example:
* var a = [];
* goog.array.extend(a, [0, 1]);
* a; // [0, 1]
* goog.array.extend(a, 2);
* a; // [0, 1, 2]
*
* @param {Array} arr1 The array to modify.
* @param {...*} var_args The elements or arrays of elements to add to arr1.
*/
goog.array.extend = function(arr1, var_args) {
for (var i = 1; i < arguments.length; i++) {
var arr2 = arguments[i];
// If we have an Array or an Arguments object we can just call push
// directly.
var isArrayLike;
if (goog.isArray(arr2) ||
// Detect Arguments. ES5 says that the [[Class]] of an Arguments object
// is "Arguments" but only V8 and JSC/Safari gets this right. We instead
// detect Arguments by checking for array like and presence of "callee".
(isArrayLike = goog.isArrayLike(arr2)) &&
// The getter for callee throws an exception in strict mode
// according to section 10.6 in ES5 so check for presence instead.
Object.prototype.hasOwnProperty.call(arr2, 'callee')) {
arr1.push.apply(arr1, arr2);
} else if (isArrayLike) {
// Otherwise loop over arr2 to prevent copying the object.
var len1 = arr1.length;
var len2 = arr2.length;
for (var j = 0; j < len2; j++) {
arr1[len1 + j] = arr2[j];
}
} else {
arr1.push(arr2);
}
}
};
/**
* Adds or removes elements from an array. This is a generic version of Array
* splice. This means that it might work on other objects similar to arrays,
* such as the arguments object.
*
* @param {goog.array.ArrayLike} arr The array to modify.
* @param {number|undefined} index The index at which to start changing the
* array. If not defined, treated as 0.
* @param {number} howMany How many elements to remove (0 means no removal. A
* value below 0 is treated as zero and so is any other non number. Numbers
* are floored).
* @param {...*} var_args Optional, additional elements to insert into the
* array.
* @return {!Array} the removed elements.
*/
goog.array.splice = function(arr, index, howMany, var_args) { goog.asserts.assert(arr.length != null);
return goog.array.ARRAY_PROTOTYPE_.splice.apply(
arr, goog.array.slice(arguments, 1));
};
/**
* Returns a new array from a segment of an array. This is a generic version of
* Array slice. This means that it might work on other objects similar to
* arrays, such as the arguments object.
*
* @param {Array.<T>|goog.array.ArrayLike} arr The array from
* which to copy a segment.
* @param {number} start The index of the first element to copy.
* @param {number=} opt_end The index after the last element to copy.
* @return {!Array.<T>} A new array containing the specified segment of the
* original array.
* @template T
*/
goog.array.slice = function(arr, start, opt_end) {
goog.asserts.assert(arr.length != null);
// passing 1 arg to slice is not the same as passing 2 where the second is
// null or undefined (in that case the second argument is treated as 0).
// we could use slice on the arguments object and then use apply instead of
// testing the length
if (arguments.length <= 2) {
return goog.array.ARRAY_PROTOTYPE_.slice.call(arr, start);
} else {
return goog.array.ARRAY_PROTOTYPE_.slice.call(arr, start, opt_end);
}
};
/**
* Removes all duplicates from an array (retaining only the first
* occurrence of each array element). This function modifies the
* array in place and doesn't change the order of the non-duplicate items.
*
* For objects, duplicates are identified as having the same unique ID as
* defined by {@link goog.getUid}.
*
* Alternatively you can specify a custom hash function that returns a unique
* value for each item in the array it should consider unique.
*
* Runtime: N,
* Worstcase space: 2N (no dupes)
*
* @param {Array.<T>|goog.array.ArrayLike} arr The array from which to remove
* duplicates.
* @param {Array=} opt_rv An optional array in which to return the results,
* instead of performing the removal inplace. If specified, the original
* array will remain unchanged.
* @param {function(T):string=} opt_hashFn An optional function to use to
* apply to every item in the array. This function should return a unique
* value for each item in the array it should consider unique.
* @template T
*/
goog.array.removeDuplicates = function(arr, opt_rv, opt_hashFn) {
var returnArray = opt_rv || arr;
var defaultHashFn = function(item) {
// Prefix each type with a single character representing the type to
// prevent conflicting keys (e.g. true and 'true').
return goog.isObject(current) ? 'o' + goog.getUid(current) :
(typeof current).charAt(0) + current;
};
var hashFn = opt_hashFn || defaultHashFn;
var seen = {}, cursorInsert = 0, cursorRead = 0; while (cursorRead < arr.length) {
var current = arr[cursorRead++];
var key = hashFn(current);
if (!Object.prototype.hasOwnProperty.call(seen, key)) {
seen[key] = true;
returnArray[cursorInsert++] = current;
}
}
returnArray.length = cursorInsert;
};
/**
* Searches the specified array for the specified target using the binary
* search algorithm. If no opt_compareFn is specified, elements are compared
* using <code>goog.array.defaultCompare</code>, which compares the elements
* using the built in < and > operators. This will produce the expected
* behavior for homogeneous arrays of String(s) and Number(s). The array
* specified <b>must</b> be sorted in ascending order (as defined by the
* comparison function). If the array is not sorted, results are undefined.
* If the array contains multiple instances of the specified target value, any
* of these instances may be found.
*
* Runtime: O(log n)
*
* @param {goog.array.ArrayLike} arr The array to be searched.
* @param {*} target The sought value.
* @param {Function=} opt_compareFn Optional comparison function by which the
* array is ordered. Should take 2 arguments to compare, and return a
* negative number, zero, or a positive number depending on whether the
* first argument is less than, equal to, or greater than the second.
* @return {number} Lowest index of the target value if found, otherwise
* (-(insertion point) - 1). The insertion point is where the value should
* be inserted into arr to preserve the sorted property. Return value >= 0
* iff target is found.
*/
goog.array.binarySearch = function(arr, target, opt_compareFn) {
return goog.array.binarySearch_(arr,
opt_compareFn || goog.array.defaultCompare, false /* isEvaluator */,
target);
};
/**
* Selects an index in the specified array using the binary search algorithm.
* The evaluator receives an element and determines whether the desired index
* is before, at, or after it. The evaluator must be consistent (formally,
* goog.array.map(goog.array.map(arr, evaluator, opt_obj), goog.math.sign)
* must be monotonically non-increasing).
*
* Runtime: O(log n)
*
* @param {goog.array.ArrayLike} arr The array to be searched.
* @param {Function} evaluator Evaluator function that receives 3 arguments
* (the element, the index and the array). Should return a negative number,
* zero, or a positive number depending on whether the desired index is
* before, at, or after the element passed to it.
* @param {Object=} opt_obj The object to be used as the value of 'this'
* within evaluator.
* @return {number} Index of the leftmost element matched by the evaluator, if
* such exists; otherwise (-(insertion point) - 1). The insertion point is
* the index of the first element for which the evaluator returns negative,
* or arr.length if no such element exists. The return value is non-negative
* iff a match is found.
*/
goog.array.binarySelect = function(arr, evaluator, opt_obj) {
return goog.array.binarySearch_(arr, evaluator, true /* isEvaluator */,
undefined /* opt_target */, opt_obj);
};
/**
* Implementation of a binary search algorithm which knows how to use both
* comparison functions and evaluators. If an evaluator is provided, will call
* the evaluator with the given optional data object, conforming to the
* interface defined in binarySelect. Otherwise, if a comparison function is
* provided, will call the comparison function against the given data object.
*
* This implementation purposefully does not use goog.bind or goog.partial for
* performance reasons.
*
* Runtime: O(log n)
*
* @param {goog.array.ArrayLike} arr The array to be searched.
* @param {Function} compareFn Either an evaluator or a comparison function,
* as defined by binarySearch and binarySelect above.
* @param {boolean} isEvaluator Whether the function is an evaluator or a
* comparison function.
* @param {*=} opt_target If the function is a comparison function, then this is
* the target to binary search for.
* @param {Object=} opt_selfObj If the function is an evaluator, this is an
* optional this object for the evaluator.
* @return {number} Lowest index of the target value if found, otherwise
* (-(insertion point) - 1). The insertion point is where the value should
* be inserted into arr to preserve the sorted property. Return value >= 0
* iff target is found.
* @private
*/
goog.array.binarySearch_ = function(arr, compareFn, isEvaluator, opt_target,
opt_selfObj) {
var left = 0; // inclusive
var right = arr.length; // exclusive
var found;
while (left < right) {
var middle = (left + right) >> 1;
var compareResult;
if (isEvaluator) {
compareResult = compareFn.call(opt_selfObj, arr[middle], middle, arr);
} else {
compareResult = compareFn(opt_target, arr[middle]);
}
if (compareResult > 0) {
left = middle + 1;
} else {
right = middle;
// We are looking for the lowest index so we can't return immediately.
found = !compareResult;
}
}
// left is the index if found, or the insertion point otherwise.
// ~left is a shorthand for -left - 1.
return found ? left : ~left;
};
/**
* Sorts the specified array into ascending order. If no opt_compareFn is
* specified, elements are compared using
* <code>goog.array.defaultCompare</code>, which compares the elements using
* the built in < and > operators. This will produce the expected behavior
* for homogeneous arrays of String(s) and Number(s), unlike the native sort,
* but will give unpredictable results for heterogenous lists of strings and
* numbers with different numbers of digits.
*
* This sort is not guaranteed to be stable.
*
* Runtime: Same as <code>Array.prototype.sort</code>
*
* @param {Array.<T>} arr The array to be sorted.
* @param {?function(T,T):number=} opt_compareFn Optional comparison * function by which the
* array is to be ordered. Should take 2 arguments to compare, and return a
* negative number, zero, or a positive number depending on whether the
* first argument is less than, equal to, or greater than the second.
* @template T
*/
goog.array.sort = function(arr, opt_compareFn) {
// TODO(arv): Update type annotation since null is not accepted.
goog.asserts.assert(arr.length != null);
goog.array.ARRAY_PROTOTYPE_.sort.call(
arr, opt_compareFn || goog.array.defaultCompare);
};
/**
* Sorts the specified array into ascending order in a stable way. If no
* opt_compareFn is specified, elements are compared using
* <code>goog.array.defaultCompare</code>, which compares the elements using
* the built in < and > operators. This will produce the expected behavior
* for homogeneous arrays of String(s) and Number(s).
*
* Runtime: Same as <code>Array.prototype.sort</code>, plus an additional
* O(n) overhead of copying the array twice.
*
* @param {Array.<T>} arr The array to be sorted.
* @param {?function(T, T): number=} opt_compareFn Optional comparison function
* by which the array is to be ordered. Should take 2 arguments to compare,
* and return a negative number, zero, or a positive number depending on
* whether the first argument is less than, equal to, or greater than the
* second.
* @template T
*/
goog.array.stableSort = function(arr, opt_compareFn) {
for (var i = 0; i < arr.length; i++) {
arr[i] = {index: i, value: arr[i]};
}
var valueCompareFn = opt_compareFn || goog.array.defaultCompare;
function stableCompareFn(obj1, obj2) {
return valueCompareFn(obj1.value, obj2.value) || obj1.index - obj2.index;
};
goog.array.sort(arr, stableCompareFn);
for (var i = 0; i < arr.length; i++) {
arr[i] = arr[i].value;
}
};
/**
* Sorts an array of objects by the specified object key and compare
* function. If no compare function is provided, the key values are
* compared in ascending order using <code>goog.array.defaultCompare</code>.
* This won't work for keys that get renamed by the compiler. So use
* {'foo': 1, 'bar': 2} rather than {foo: 1, bar: 2}.
* @param {Array.<Object>} arr An array of objects to sort.
* @param {string} key The object key to sort by.
* @param {Function=} opt_compareFn The function to use to compare key
* values.
*/
goog.array.sortObjectsByKey = function(arr, key, opt_compareFn) {
var compare = opt_compareFn || goog.array.defaultCompare;
goog.array.sort(arr, function(a, b) {
return compare(a[key], b[key]);
});
};
/**
* Tells if the array is sorted.
* @param {!Array.<T>} arr The array. * @param {?function(T,T):number=} opt_compareFn Function to compare the
* array elements.
* Should take 2 arguments to compare, and return a negative number, zero,
* or a positive number depending on whether the first argument is less
* than, equal to, or greater than the second.
* @param {boolean=} opt_strict If true no equal elements are allowed.
* @return {boolean} Whether the array is sorted.
* @template T
*/
goog.array.isSorted = function(arr, opt_compareFn, opt_strict) {
var compare = opt_compareFn || goog.array.defaultCompare;
for (var i = 1; i < arr.length; i++) {
var compareResult = compare(arr[i - 1], arr[i]);
if (compareResult > 0 || compareResult == 0 && opt_strict) {
return false;
}
}
return true;
};
/**
* Compares two arrays for equality. Two arrays are considered equal if they
* have the same length and their corresponding elements are equal according to
* the comparison function.
*
* @param {goog.array.ArrayLike} arr1 The first array to compare.
* @param {goog.array.ArrayLike} arr2 The second array to compare.
* @param {Function=} opt_equalsFn Optional comparison function.
* Should take 2 arguments to compare, and return true if the arguments
* are equal. Defaults to {@link goog.array.defaultCompareEquality} which
* compares the elements using the built-in '===' operator.
* @return {boolean} Whether the two arrays are equal.
*/
goog.array.equals = function(arr1, arr2, opt_equalsFn) {
if (!goog.isArrayLike(arr1) || !goog.isArrayLike(arr2) ||
arr1.length != arr2.length) {
return false;
}
var l = arr1.length;
var equalsFn = opt_equalsFn || goog.array.defaultCompareEquality;
for (var i = 0; i < l; i++) {
if (!equalsFn(arr1[i], arr2[i])) {
return false;
}
}
return true;
};
/**
* @deprecated Use {@link goog.array.equals}.
* @param {goog.array.ArrayLike} arr1 See {@link goog.array.equals}.
* @param {goog.array.ArrayLike} arr2 See {@link goog.array.equals}.
* @param {Function=} opt_equalsFn See {@link goog.array.equals}.
* @return {boolean} See {@link goog.array.equals}.
*/
goog.array.compare = function(arr1, arr2, opt_equalsFn) {
return goog.array.equals(arr1, arr2, opt_equalsFn);
};
/**
* 3-way array compare function.
* @param {!goog.array.ArrayLike} arr1 The first array to compare.
* @param {!goog.array.ArrayLike} arr2 The second array to compare.
* @param {?function(?, ?): number=} opt_compareFn Optional comparison function
* by which the array is to be ordered. Should take 2 arguments to compare,
* and return a negative number, zero, or a positive number depending on
* whether the first argument is less than, equal to, or greater than the * second.
* @return {number} Negative number, zero, or a positive number depending on
* whether the first argument is less than, equal to, or greater than the
* second.
*/
goog.array.compare3 = function(arr1, arr2, opt_compareFn) {
var compare = opt_compareFn || goog.array.defaultCompare;
var l = Math.min(arr1.length, arr2.length);
for (var i = 0; i < l; i++) {
var result = compare(arr1[i], arr2[i]);
if (result != 0) {
return result;
}
}
return goog.array.defaultCompare(arr1.length, arr2.length);
};
/**
* Compares its two arguments for order, using the built in < and >
* operators.
* @param {*} a The first object to be compared.
* @param {*} b The second object to be compared.
* @return {number} A negative number, zero, or a positive number as the first
* argument is less than, equal to, or greater than the second.
*/
goog.array.defaultCompare = function(a, b) {
return a > b ? 1 : a < b ? -1 : 0;
};
/**
* Compares its two arguments for equality, using the built in === operator.
* @param {*} a The first object to compare.
* @param {*} b The second object to compare.
* @return {boolean} True if the two arguments are equal, false otherwise.
*/
goog.array.defaultCompareEquality = function(a, b) {
return a === b;
};
/**
* Inserts a value into a sorted array. The array is not modified if the
* value is already present.
* @param {Array.<T>} array The array to modify.
* @param {T} value The object to insert.
* @param {?function(T,T):number=} opt_compareFn Optional comparison function by
* which the
* array is ordered. Should take 2 arguments to compare, and return a
* negative number, zero, or a positive number depending on whether the
* first argument is less than, equal to, or greater than the second.
* @return {boolean} True if an element was inserted.
* @template T
*/
goog.array.binaryInsert = function(array, value, opt_compareFn) {
var index = goog.array.binarySearch(array, value, opt_compareFn);
if (index < 0) {
goog.array.insertAt(array, value, -(index + 1));
return true;
}
return false;
};
/**
* Removes a value from a sorted array.
* @param {Array} array The array to modify.
* @param {*} value The object to remove.
* @param {Function=} opt_compareFn Optional comparison function by which the * array is ordered. Should take 2 arguments to compare, and return a
* negative number, zero, or a positive number depending on whether the
* first argument is less than, equal to, or greater than the second.
* @return {boolean} True if an element was removed.
*/
goog.array.binaryRemove = function(array, value, opt_compareFn) {
var index = goog.array.binarySearch(array, value, opt_compareFn);
return (index >= 0) ? goog.array.removeAt(array, index) : false;
};
/**
* Splits an array into disjoint buckets according to a splitting function.
* @param {Array.<T>} array The array.
* @param {function(this:S, T,number,Array.<T>):?} sorter Function to call for
* every element. This takes 3 arguments (the element, the index and the
* array) and must return a valid object key (a string, number, etc), or
* undefined, if that object should not be placed in a bucket.
* @param {S=} opt_obj The object to be used as the value of 'this' within
* sorter.
* @return {!Object} An object, with keys being all of the unique return values
* of sorter, and values being arrays containing the items for
* which the splitter returned that key.
* @template T,S
*/
goog.array.bucket = function(array, sorter, opt_obj) {
var buckets = {};
for (var i = 0; i < array.length; i++) {
var value = array[i];
var key = sorter.call(opt_obj, value, i, array);
if (goog.isDef(key)) {
// Push the value to the right bucket, creating it if necessary.
var bucket = buckets[key] || (buckets[key] = []);
bucket.push(value);
}
}
return buckets;
};
/**
* Creates a new object built from the provided array and the key-generation
* function.
* @param {Array.<T>|goog.array.ArrayLike} arr Array or array like object over
* which to iterate whose elements will be the values in the new object.
* @param {?function(this:S, T, number, ?) : string} keyFunc The function to
* call for every element. This function takes 3 arguments (the element, the
* index and the array) and should return a string that will be used as the
* key for the element in the new object. If the function returns the same
* key for more than one element, the value for that key is
* implementation-defined.
* @param {S=} opt_obj The object to be used as the value of 'this'
* within keyFunc.
* @return {!Object.<T>} The new object.
* @template T,S
*/
goog.array.toObject = function(arr, keyFunc, opt_obj) {
var ret = {};
goog.array.forEach(arr, function(element, index) {
ret[keyFunc.call(opt_obj, element, index, arr)] = element;
});
return ret;
};
/**
* Creates a range of numbers in an arithmetic progression.
* * Range takes 1, 2, or 3 arguments:
* <pre>
* range(5) is the same as range(0, 5, 1) and produces [0, 1, 2, 3, 4]
* range(2, 5) is the same as range(2, 5, 1) and produces [2, 3, 4]
* range(-2, -5, -1) produces [-2, -3, -4]
* range(-2, -5, 1) produces [], since stepping by 1 wouldn't ever reach -5.
* </pre>
*
* @param {number} startOrEnd The starting value of the range if an end argument
* is provided. Otherwise, the start value is 0, and this is the end value.
* @param {number=} opt_end The optional end value of the range.
* @param {number=} opt_step The step size between range values. Defaults to 1
* if opt_step is undefined or 0.
* @return {!Array.<number>} An array of numbers for the requested range. May be
* an empty array if adding the step would not converge toward the end
* value.
*/
goog.array.range = function(startOrEnd, opt_end, opt_step) {
var array = [];
var start = 0;
var end = startOrEnd;
var step = opt_step || 1;
if (opt_end !== undefined) {
start = startOrEnd;
end = opt_end;
}
if (step * (end - start) < 0) {
// Sign mismatch: start + step will never reach the end value.
return [];
}
if (step > 0) {
for (var i = start; i < end; i += step) {
array.push(i);
}
} else {
for (var i = start; i > end; i += step) {
array.push(i);
}
}
return array;
};
/**
* Returns an array consisting of the given value repeated N times.
*
* @param {*} value The value to repeat.
* @param {number} n The repeat count.
* @return {!Array} An array with the repeated value.
*/
goog.array.repeat = function(value, n) {
var array = [];
for (var i = 0; i < n; i++) {
array[i] = value;
}
return array;
};
/**
* Returns an array consisting of every argument with all arrays
* expanded in-place recursively.
*
* @param {...*} var_args The values to flatten.
* @return {!Array} An array containing the flattened values.
*/
goog.array.flatten = function(var_args) {
var result = []; for (var i = 0; i < arguments.length; i++) {
var element = arguments[i];
if (goog.isArray(element)) {
result.push.apply(result, goog.array.flatten.apply(null, element));
} else {
result.push(element);
}
}
return result;
};
/**
* Rotates an array in-place. After calling this method, the element at
* index i will be the element previously at index (i - n) %
* array.length, for all values of i between 0 and array.length - 1,
* inclusive.
*
* For example, suppose list comprises [t, a, n, k, s]. After invoking
* rotate(array, 1) (or rotate(array, -4)), array will comprise [s, t, a, n, k].
*
* @param {!Array.<T>} array The array to rotate.
* @param {number} n The amount to rotate.
* @return {!Array.<T>} The array.
* @template T
*/
goog.array.rotate = function(array, n) {
goog.asserts.assert(array.length != null);
if (array.length) {
n %= array.length;
if (n > 0) {
goog.array.ARRAY_PROTOTYPE_.unshift.apply(array, array.splice(-n, n));
} else if (n < 0) {
goog.array.ARRAY_PROTOTYPE_.push.apply(array, array.splice(0, -n));
}
}
return array;
};
/**
* Moves one item of an array to a new position keeping the order of the rest
* of the items. Example use case: keeping a list of JavaScript objects
* synchronized with the corresponding list of DOM elements after one of the
* elements has been dragged to a new position.
* @param {!(Array|Arguments|{length:number})} arr The array to modify.
* @param {number} fromIndex Index of the item to move between 0 and
* {@code arr.length - 1}.
* @param {number} toIndex Target index between 0 and {@code arr.length - 1}.
*/
goog.array.moveItem = function(arr, fromIndex, toIndex) {
goog.asserts.assert(fromIndex >= 0 && fromIndex < arr.length);
goog.asserts.assert(toIndex >= 0 && toIndex < arr.length);
// Remove 1 item at fromIndex.
var removedItems = goog.array.ARRAY_PROTOTYPE_.splice.call(arr, fromIndex, 1);
// Insert the removed item at toIndex.
goog.array.ARRAY_PROTOTYPE_.splice.call(arr, toIndex, 0, removedItems[0]);
// We don't use goog.array.insertAt and goog.array.removeAt, because they're
// significantly slower than splice.
};
/**
* Creates a new array for which the element at position i is an array of the
* ith element of the provided arrays. The returned array will only be as long
* as the shortest array provided; additional values are ignored. For example,
* the result of zipping [1, 2] and [3, 4, 5] is [[1,3], [2, 4]].
*
* This is similar to the zip() function in Python. See {@link * http://docs.python.org/library/functions.html#zip}
*
* @param {...!goog.array.ArrayLike} var_args Arrays to be combined.
* @return {!Array.<!Array>} A new array of arrays created from provided arrays.
*/
goog.array.zip = function(var_args) {
if (!arguments.length) {
return [];
}
var result = [];
for (var i = 0; true; i++) {
var value = [];
for (var j = 0; j < arguments.length; j++) {
var arr = arguments[j];
// If i is larger than the array length, this is the shortest array.
if (i >= arr.length) {
return result;
}
value.push(arr[i]);
}
result.push(value);
}
};
/**
* Shuffles the values in the specified array using the Fisher-Yates in-place
* shuffle (also known as the Knuth Shuffle). By default, calls Math.random()
* and so resets the state of that random number generator. Similarly, may reset
* the state of the any other specified random number generator.
*
* Runtime: O(n)
*
* @param {!Array} arr The array to be shuffled.
* @param {function():number=} opt_randFn Optional random function to use for
* shuffling.
* Takes no arguments, and returns a random number on the interval [0, 1).
* Defaults to Math.random() using JavaScript's built-in Math library.
*/
goog.array.shuffle = function(arr, opt_randFn) {
var randFn = opt_randFn || Math.random;
for (var i = arr.length - 1; i > 0; i--) {
// Choose a random array index in [0, i] (inclusive with i).
var j = Math.floor(randFn() * (i + 1));
var tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
};