Array.html
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<pre class="prettyprint lang-js"><span id='Array'>/**
</span> * @class Array
*
* In JavaScript, the `Array` property of the global object is a constructor for
* array instances.
*
* An array is a JavaScript object. Note that you shouldn't use it as an
* associative array, use {@link Object} instead.
*
* # Creating an Array
*
* The following example creates an array, msgArray, with a length of 0, then assigns values to
* msgArray[0] and msgArray[99], changing the length of the array to 100.
*
* var msgArray = new Array();
* msgArray[0] = "Hello";
* msgArray[99] = "world";
*
* if (msgArray.length == 100)
* print("The length is 100.");
*
* # Creating a Two-dimensional Array
*
* The following creates chess board as a two dimensional array of strings. The first move is made by
* copying the 'P' in 6,4 to 4,4. The position 4,4 is left blank.
*
* var board =
* [ ['R','N','B','Q','K','B','N','R'],
* ['P','P','P','P','P','P','P','P'],
* [' ',' ',' ',' ',' ',' ',' ',' '],
* [' ',' ',' ',' ',' ',' ',' ',' '],
* [' ',' ',' ',' ',' ',' ',' ',' '],
* [' ',' ',' ',' ',' ',' ',' ',' '],
* ['p','p','p','p','p','p','p','p'],
* ['r','n','b','q','k','b','n','r']];
* print(board.join('\n') + '\n\n');
*
* // Move King's Pawn forward 2
* board[4][4] = board[6][4];
* board[6][4] = ' ';
* print(board.join('\n'));
*
* Here is the output:
*
* R,N,B,Q,K,B,N,R
* P,P,P,P,P,P,P,P
* , , , , , , ,
* , , , , , , ,
* , , , , , , ,
* , , , , , , ,
* p,p,p,p,p,p,p,p
* r,n,b,q,k,b,n,r
*
* R,N,B,Q,K,B,N,R
* P,P,P,P,P,P,P,P
* , , , , , , ,
* , , , , , , ,
* , , , ,p, , ,
* , , , , , , ,
* p,p,p,p, ,p,p,p
* r,n,b,q,k,b,n,r
*
* # Accessing array elements
*
* Array elements are nothing less than object properties, so they are accessed as such.
*
* var myArray = new Array("Wind", "Rain", "Fire");
* myArray[0]; // "Wind"
* myArray[1]; // "Rain"
* // etc.
* myArray.length; // 3
*
* // Even if indices are properties, the following notation throws a syntax error
* myArray.2;
*
* // It should be noted that in JavaScript, object property names are strings. Consequently,
* myArray[0] === myArray["0"];
* myArray[1] === myArray["1"];
* // etc.
*
* // However, this should be considered carefully
* myArray[02]; // "Fire". The number 02 is converted as the "2" string
* myArray["02"]; // undefined. There is no property named "02"
*
* # Relationship between length and numerical properties
*
* An array's length property and numerical properties are connected. Here is some
* code explaining how this relationship works.
*
* var a = [];
*
* a[0] = 'a';
* console.log(a[0]); // 'a'
* console.log(a.length); // 1
*
* a[1] = 32;
* console.log(a[1]); // 32
* console.log(a.length); // 2
*
* a[13] = 12345;
* console.log(a[13]); // 12345
* console.log(a.length); // 14
*
* a.length = 10;
* console.log(a[13]); // undefined, when reducing the length elements after length+1 are removed
* console.log(a.length); // 10
*
* # Creating an array using the result of a match
*
* The result of a match between a regular expression and a string can create an array.
* This array has properties and elements that provide information about the match. An
* array is the return value of RegExp.exec, String.match, and String.replace. To help
* explain these properties and elements, look at the following example and then refer
* to the table below:
*
* // Match one d followed by one or more b's followed by one d
* // Remember matched b's and the following d
* // Ignore case
*
* var myRe = /d(b+)(d)/i;
* var myArray = myRe.exec("cdbBdbsbz");
*
* The properties and elements returned from this match are as follows:
*
*
* | Property/Element | Description | Example
* |:-----------------|:--------------------------------------------------------------------------------------|:-------------------
* | `input` | A read-only property that reflects the original string against which the | cdbBdbsbz
* | | regular expression was matched. |
* | `index` | A read-only property that is the zero-based index of the match in the string. | 1
* | `[0]` | A read-only element that specifies the last matched characters. | dbBd
* | `[1], ...[n]` | Read-only elements that specify the parenthesized substring matches, if included in | [1]: bB [2]: d
* | | the regular expression. The number of possible parenthesized substrings is unlimited. |
*
* <div class="notice">
* Documentation for this class comes from <a href="https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array">MDN</a>
* and is available under <a href="http://creativecommons.org/licenses/by-sa/2.0/">Creative Commons: Attribution-Sharealike license</a>.
* </div>
*
*/
<span id='Array-method-constructor'>/**
</span> * @method constructor
* Creates new Array object.
*
* @param {Number/Object...} items Either a number that specifies the length of array or any number of items
* for the array.
*/
// Properties
<span id='Array-property-length'>/**
</span> * @property {Number} length
* Reflects the number of elements in an array.
*
* The value of the `length` property is an integer with a positive sign and a value less than 2 to the 32
* power (232).
*
* You can set the `length` property to truncate an array at any time. When you extend an array by changing
* its `length` property, the number of actual elements does not increase; for example, if you set `length`
* to 3 when it is currently 2, the array still contains only 2 elements.
*
* In the following example the array numbers is iterated through by looking at the `length` property to see
* how many elements it has. Each value is then doubled.
*
* var numbers = [1,2,3,4,5];
* for (var i = 0; i < numbers.length; i++) {
* numbers[i] *= 2;
* }
* // numbers is now [2,4,6,8,10];
*
* The following example shortens the array `statesUS` to a length of 50 if the current `length` is greater
* than 50.
*
* if (statesUS.length > 50) {
* statesUS.length=50
* }
*/
// Mutator methods. These methods modify the array:
<span id='Array-method-pop'>/**
</span> * @method pop
* The pop method removes the last element from an array and returns that value to the caller.
*
* `pop` is intentionally generic; this method can be called or applied to objects resembling
* arrays. Objects which do not contain a length property reflecting the last in a series of
* consecutive, zero-based numerical properties may not behave in any meaningful manner.
*
* var myFish = ["angel", "clown", "mandarin", "surgeon"];
* var popped = myFish.pop();
* alert(popped); // Alerts 'surgeon'
*
* @return {Object} The last element in the array
*/
<span id='Array-method-push'>/**
</span> * @method push
* Adds one or more elements to the end of an array and returns the new length of the array.
*
* `push` is intentionally generic. This method can be called or applied to objects resembling
* arrays. The push method relies on a length property to determine where to start inserting
* the given values. If the length property cannot be converted into a number, the index used
* is 0. This includes the possibility of length being nonexistent, in which case length will
* also be created.
*
* The only native, array-like objects are strings, although they are not suitable in
* applications of this method, as strings are immutable.
*
* ### Adding elements to an array
*
* The following code creates the sports array containing two elements, then appends two elements
* to it. After the code executes, sports contains 4 elements: "soccer", "baseball", "football"
* and "swimming".
*
* var sports = ["soccer", "baseball"];
* sports.push("football", "swimming");
*
* @param {Object...} elements The elements to add to the end of the array.
* @return {Number} The new length property of the object upon which the method was called.
*/
<span id='Array-method-reverse'>/**
</span> * @method reverse
* Reverses the order of the elements of an array -- the first becomes the last, and the
* last becomes the first.
*
* The reverse method transposes the elements of the calling array object in place, mutating the
* array, and returning a reference to the array.
*
* The following example creates an array myArray, containing three elements, then reverses the array.
*
* var myArray = ["one", "two", "three"];
* myArray.reverse();
*
* This code changes myArray so that:
*
* - myArray[0] is "three"
* - myArray[1] is "two"
* - myArray[2] is "one"
*
* @return {Array} A reference to the array
*/
<span id='Array-method-shift'>/**
</span> * @method shift
* Removes the first element from an array and returns that element.
*
* The `shift` method removes the element at the zeroeth index and shifts the values at consecutive
* indexes down, then returns the removed value.
*
* `shift` is intentionally generic; this method can be called or applied to objects resembling
* arrays. Objects which do not contain a `length` property reflecting the last in a series of
* consecutive, zero-based numerical properties may not behave in any meaningful manner.
*
* The following code displays the `myFish` array before and after removing its first element. It also
* displays the removed element:
*
* // assumes a println function is defined
* var myFish = ["angel", "clown", "mandarin", "surgeon"];
* println("myFish before: " + myFish);
* var shifted = myFish.shift();
* println("myFish after: " + myFish);
* println("Removed this element: " + shifted);
*
* This example displays the following:
*
* myFish before: angel,clown,mandarin,surgeon
* myFish after: clown,mandarin,surgeon
* Removed this element: angel
*
* @return {Object} The first element of the array prior to shifting.
*/
<span id='Array-method-sort'>/**
</span> * @method sort
* Sorts the elements of an array.
*
* If `compareFunction` is not supplied, elements are sorted by converting them to strings and
* comparing strings in lexicographic ("dictionary" or "telephone book," not numerical) order. For
* example, "80" comes before "9" in lexicographic order, but in a numeric sort 9 comes before 80.
*
* If `compareFunction` is supplied, the array elements are sorted according to the return value of
* the compare function. If a and b are two elements being compared, then:
* If `compareFunction(a, b)` is less than 0, sort `a` to a lower index than `b`.
* If `compareFunction(a, b)` returns 0, leave `a` and `b` unchanged with respect to each other, but
* sorted with respect to all different elements. Note: the ECMAscript standard does not guarantee
* this behaviour, and thus not all browsers respect this.
* If `compareFunction(a, b)` is greater than 0, sort `b` to a lower index than `a`.
* `compareFunction(a, b)` must always returns the same value when given a specific pair of elements a
* and b as its two arguments. If inconsistent results are returned then the sort order is undefined
*
* So, the compare function has the following form:
*
* function compare(a, b)
* {
* if (a is less than b by some ordering criterion)
* return -1;
* if (a is greater than b by the ordering criterion)
* return 1;
* // a must be equal to b
* return 0;
* }
*
* To compare numbers instead of strings, the compare function can simply subtract `b` from `a`:
*
* function compareNumbers(a, b)
* {
* return a - b;
* }
*
* The sort() method can be conveniently used with closures:
*
* var numbers = [4, 2, 5, 1, 3];
* numbers.sort(function(a, b) {
* return a - b;
* });
* print(numbers);
*
* @param {Function} compareFunction Specifies a function that defines the sort order. If omitted, the
* array is sorted lexicographically (in dictionary order) according to the string conversion of each
* element.
* @return {Array} A reference to the array
*/
<span id='Array-method-splice'>/**
</span> * @method splice
* Adds and/or removes elements from an array.
*
* If you specify a different number of elements to insert than the number you're removing, the array
* will have a different length at the end of the call.
*
* // assumes a print function is defined
* var myFish = ["angel", "clown", "mandarin", "surgeon"];
* print("myFish: " + myFish);
*
* var removed = myFish.splice(2, 0, "drum");
* print("After adding 1: " + myFish);
* print("removed is: " + removed);
*
* removed = myFish.splice(3, 1);
* print("After removing 1: " + myFish);
* print("removed is: " + removed);
*
* removed = myFish.splice(2, 1, "trumpet");
* print("After replacing 1: " + myFish);
* print("removed is: " + removed);
*
* removed = myFish.splice(0, 2, "parrot", "anemone", "blue");
* print("After replacing 2: " + myFish);
* print("removed is: " + removed);
*
* This script displays:
*
* myFish: angel,clown,mandarin,surgeon
* After adding 1: angel,clown,drum,mandarin,surgeon
* removed is:
* After removing 1: angel,clown,drum,surgeon
* removed is: mandarin
* After replacing 1: angel,clown,trumpet,surgeon
* removed is: drum
* After replacing 2: parrot,anemone,blue,trumpet,surgeon
* removed is: angel,clown
*
* @param {Number} index Index at which to start changing the array. If negative, will begin that
* many elements from the end.
* @param {Number} howMany An integer indicating the number of old array elements to remove. If
* `howMany` is 0, no elements are removed. In this case, you should specify at least one new element.
* If no `howMany` parameter is specified all elements after index are removed.
* @param {Object...} elements The elements to add to the array. If you don't specify any
* elements, `splice` simply removes elements from the array.
* @return {Array} An array containing the removed elements. If only one element is removed, an array
* of one element is returned..
*/
<span id='Array-method-unshift'>/**
</span> * @method unshift
* Adds one or more elements to the front of an array and returns the new length of the array.
*
* The `unshift` method inserts the given values to the beginning of an array-like object.
*
* `unshift` is intentionally generic; this method can be called or applied to objects resembling
* arrays. Objects which do not contain a `length` property reflecting the last in a series of
* consecutive, zero-based numerical properties may not behave in any meaningful manner.
*
* The following code displays the myFish array before and after adding elements to it.
*
* // assumes a println function exists
* myFish = ["angel", "clown"];
* println("myFish before: " + myFish);
* unshifted = myFish.unshift("drum", "lion");
* println("myFish after: " + myFish);
* println("New length: " + unshifted);
*
* This example displays the following:
*
* myFish before: ["angel", "clown"]
* myFish after: ["drum", "lion", "angel", "clown"]
* New length: 4
*
* @param {Object...} elements The elements to add to the front of the array.
* @return {Number} The array's new length.
*/
// Accessor methods. These methods do not modify the array and return some representation of the array.
<span id='Array-method-concat'>/**
</span> * @method concat
* Returns a new array comprised of this array joined with other array(s) and/or value(s).
*
* `concat` creates a new array consisting of the elements in the `this` object on which it is called,
* followed in order by, for each argument, the elements of that argument (if the argument is an
* array) or the argument itself (if the argument is not an array).
*
* `concat` does not alter `this` or any of the arrays provided as arguments but instead returns a
* "one level deep" copy that contains copies of the same elements combined from the original arrays.
* Elements of the original arrays are copied into the new array as follows:
* Object references (and not the actual object): `concat` copies object references into the new
* array. Both the original and new array refer to the same object. That is, if a referenced object is
* modified, the changes are visible to both the new and original arrays.
* Strings and numbers (not {@link String} and {@link Number} objects): `concat` copies the values of
* strings and numbers into the new array.
*
* Any operation on the new array will have no effect on the original arrays, and vice versa.
*
* ### Concatenating two arrays
*
* The following code concatenates two arrays:
*
* var alpha = ["a", "b", "c"];
* var numeric = [1, 2, 3];
*
* // creates array ["a", "b", "c", 1, 2, 3]; alpha and numeric are unchanged
* var alphaNumeric = alpha.concat(numeric);
*
* ### Concatenating three arrays
*
* The following code concatenates three arrays:
*
* var num1 = [1, 2, 3];
* var num2 = [4, 5, 6];
* var num3 = [7, 8, 9];
*
* // creates array [1, 2, 3, 4, 5, 6, 7, 8, 9]; num1, num2, num3 are unchanged
* var nums = num1.concat(num2, num3);
*
* ### Concatenating values to an array
*
* The following code concatenates three values to an array:
*
* var alpha = ['a', 'b', 'c'];
*
* // creates array ["a", "b", "c", 1, 2, 3], leaving alpha unchanged
* var alphaNumeric = alpha.concat(1, [2, 3]);
*
* @param {Object...} values Arrays and/or values to concatenate to the resulting array.
* @return {Array} New array.
*/
<span id='Array-method-join'>/**
</span> * @method join
* Joins all elements of an array into a string.
*
* The string conversions of all array elements are joined into one string.
*
* The following example creates an array, `a`, with three elements, then joins the array three times:
* using the default separator, then a comma and a space, and then a plus.
*
* var a = new Array("Wind","Rain","Fire");
* var myVar1 = a.join(); // assigns "Wind,Rain,Fire" to myVar1
* var myVar2 = a.join(", "); // assigns "Wind, Rain, Fire" to myVar2
* var myVar3 = a.join(" + "); // assigns "Wind + Rain + Fire" to myVar3
*
* @param {String} separator Specifies a string to separate each element of the array. The separator
* is converted to a string if necessary. If omitted, the array elements are separated with a comma.
* @return {String} A string of the array elements.
*/
<span id='Array-method-slice'>/**
</span> * @method slice
* Extracts a section of an array and returns a new array.
*
* `slice` does not alter the original array, but returns a new "one level deep" copy that contains
* copies of the elements sliced from the original array. Elements of the original array are copied
* into the new array as follows:
* * For object references (and not the actual object), `slice` copies object references into the
* new array. Both the original and new array refer to the same object. If a referenced object
* changes, the changes are visible to both the new and original arrays.
* * For strings and numbers (not {@link String} and {@link Number} objects), `slice` copies strings
* and numbers into the new array. Changes to the string or number in one array does not affect the
* other array.
*
* If a new element is added to either array, the other array is not affected.
*
* ### Using slice
*
* In the following example, `slice` creates a new array, `newCar`, from `myCar`. Both include a
* reference to the object `myHonda`. When the color of `myHonda` is changed to purple, both arrays
* reflect the change.
*
* // Using slice, create newCar from myCar.
* var myHonda = { color: "red", wheels: 4, engine: { cylinders: 4, size: 2.2 } };
* var myCar = [myHonda, 2, "cherry condition", "purchased 1997"];
* var newCar = myCar.slice(0, 2);
*
* // Print the values of myCar, newCar, and the color of myHonda
* // referenced from both arrays.
* print("myCar = " + myCar.toSource());
* print("newCar = " + newCar.toSource());
* print("myCar[0].color = " + myCar[0].color);
* print("newCar[0].color = " + newCar[0].color);
*
* // Change the color of myHonda.
* myHonda.color = "purple";
* print("The new color of my Honda is " + myHonda.color);
*
* // Print the color of myHonda referenced from both arrays.
* print("myCar[0].color = " + myCar[0].color);
* print("newCar[0].color = " + newCar[0].color);
*
* This script writes:
*
* myCar = [{color:"red", wheels:4, engine:{cylinders:4, size:2.2}}, 2, "cherry condition",
* "purchased 1997"]
* newCar = [{color:"red", wheels:4, engine:{cylinders:4, size:2.2}}, 2]
* myCar[0].color = red
* newCar[0].color = red
* The new color of my Honda is purple
* myCar[0].color = purple
* newCar[0].color = purple
*
* @param {Number} begin Zero-based index at which to begin extraction.
* As a negative index, `start` indicates an offset from the end of the sequence. `slice(-2)` extracts
* the second-to-last element and the last element in the sequence
* @param {Number} end Zero-based index at which to end extraction. `slice` extracts up to but not
* including `end`.
* `slice(1,4)` extracts the second element through the fourth element (elements indexed 1, 2, and 3).
* As a negative index, end indicates an offset from the end of the sequence. `slice(2,-1)` extracts
* the third element through the second-to-last element in the sequence.
* If `end` is omitted, `slice` extracts to the end of the sequence.
* @return {Array} Array from the new start position up to (but not including) the specified end position.
*/
<span id='Array-method-toString'>/**
</span> * @method toString
* Returns a string representing the array and its elements. Overrides the `Object.prototype.toString`
* method.
*
* The {@link Array} object overrides the `toString` method of {@link Object}. For Array objects, the
* `toString` method joins the array and returns one string containing each array element separated by
* commas. For example, the following code creates an array and uses `toString` to convert the array
* to a string.
*
* var monthNames = new Array("Jan","Feb","Mar","Apr");
* myVar = monthNames.toString(); // assigns "Jan,Feb,Mar,Apr" to myVar
*
* JavaScript calls the `toString` method automatically when an array is to be represented as a text
* value or when an array is referred to in a string concatenation.
*
* @return {String} The array as a string.
*/</pre>
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