Array

  • Raccourci de la révision : JavaScript/Reference/Global_Objects/Array
  • Titre de la révision : Array
  • ID de la révision : 499827
  • Créé :
  • Créateur : antham
  • Version actuelle ? Non
  • Commentaire

Contenu de la révision

Résumé

L'objet global Array est un constructeur de tableaux, qui correspondent à des objets de haut niveau s'apparentant aux listes.

Syntaxe

[element0, element1, ..., elementN]
new Array(element0, element1, ..., elementN)
new Array(arrayLength)
element0, element1, ..., elementN
Un tableau en javascript est initialisé avec les éléments passés en paramètre, à l'exception du cas où un seul argument est passé au constructeur de l'objet Array et que cet argument est un chiffre. (Voi ci-dessous.) A noter que ce cas particulié s'applique aux tableaux créent avec le constructeur de l'objet Array , non pas aux tableaux litérales créent avec la syntaxe des crochets.
arrayLength
Si le seul argument passé au constructeur de l'objet Array  est un entier entre 0 et 232-1 (inclus), un nouveau tableau vide est retourné avec sa taille défini par cet entier et contenant autant d'entrées, chacune étant initialisée à undefined. Si l'argument est n'importe quel autre nombre, une exception RangeError est levée.

Description

Les tableaux sont des objets s'apparentant aux listes qui possèdent plusieurs méthodes de base pour exécuter des opérations de parcours et de mutation. Ni la taille du tableau en Javascript ni le type de ses éléments n'est dixé. Comme la taille d'un tableau peut augmenter ou diminuer à n'importe quel moment, les tableaux en Javascript ne sont pas garantis denses. Globalement, ce sont des charactéristiques utiles; mais si c'est fonctionnalité ne sont pas souhaitable pour votre cas d'utilisation, vous pouvez considérer l'utilisation de tableaux de type WebGL.

Note that you shouldn't use an array as an associative array. You can use plain objects instead, although doing so comes with its own caveats. See the post Lightweight JavaScript dictionaries with arbitrary keys as an example.

Accessing array elements

JavaScript arrays are zero-indexed; the first element of an array is actually at index 0, and the last element is at the index equal to the value of the array's length property minus 1.

var arr = ["this is the first element", "this is the second element"];
console.log(arr[0]);              // prints "this is the first element"
console.log(arr[1]);              // prints "this is the second element"
console.log(arr[arr.length - 1]); // prints "this is the second element"

Array elements are just object properties, in the way that toString is a property. However, note that trying to access the first element of an array as follows will throw a syntax error:

console.log(arr.0);

Note that there is nothing unique about JavaScript arrays and their properties that causes this. JavaScript properties that begin with a digit cannot be referenced with dot notation. They must be accessed using bracket notation. For example, if you had an object with a property "3d", it too would have to be referenced using bracket notation, not dot notation. This similarity is exhibited in the following two code samples:

var years = [1950, 1960, 1970, 1980, 1990, 2000, 2010];
try {
  console.log(years.0);
}
catch (ex) {
  console.log("Using bracket notation");
  console.log(years[0]);
}
try {
  renderer.3d.setTexture(model, "character.png");
}
catch (ex) {
  console.log("Using bracket notation");
  renderer["3d"].setTexture(model, "character.png");
}

Note that in the 3d example, "3d" had to be quoted. It's possible to quote the JavaScript array indexes as well (e.g., years["2"] instead of years[2]), although it's not necessary. The 2 in years[2] eventually gets coerced into a string by the JavaScript engine, anyway, through an implicit toString conversion. It is for this reason that "2" and "02" would refer to two different slots on the years object and the following example logs true:

console.log(years["2"] != years["02"]);

Relationship between length and numerical properties

A JavaScript array's length property and numerical properties are connected. Several of the built-in array methods (e.g., join, slice, indexOf, etc.) take into account the value of an array's length property when they're called. Other methods (e.g., push, splice, etc.) also result in updates to an array's length property.

var fruits = [];
fruits.push("banana", "apple", "peach");

console.log(fruits.length); // 3

When setting a property on a JavaScript array when the property is a valid array index and that index is outside the current bounds of the array, the array will grow to a size large enough to accommodate an element at that index, and the engine will update the array's length property accordingly:

fruits[3] = "mango";
console.log(fruits[3]);
console.log(fruits.length); // 4

Setting the length property, directly, also results in special behavior.

fruits.length = 10;
console.log(fruits);        // The array gets padded with undefined
console.log(fruits.length); // 10

This is explained further on the length page.

Creating an array using the result of a match

The result of a match between a regular expression and a string can create a JavaScript 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 regular expression was matched. cdbBdbsbz
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 the regular expression. The number of possible parenthesized substrings is unlimited. [1]: bB
[2]: d

Properties

{{ Js_see_prototype("Array", "Properties") }}

prototype
Allows the addition of properties to all objects.
{{ jsOverrides("Function", "Properties", "prototype") }}

Methods

{{ Js_see_prototype("Array", "Methods") }}
isArray {{ js_minversion_inline("1.8.5") }}
Return true if a variable is an array, if not false.

Array instances

Array instances inherit from Array.prototype. As with all constructors, you can change the constructor's prototype object to make changes to all JavaScript Array instances.

Properties

{{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Properties') }}

Methods

Mutator methods

{{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Mutator_methods') }}

Accessor methods

{{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Accessor_methods') }}

Iteration methods

{{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Iteration_methods') }}

Examples

Example: 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.");

Example: 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 old position 6,4 is made 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

Browser compatibility

{{ CompatibilityTable }}

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }}
Feature Android Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile
Basic support {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }} {{ CompatVersionUnknown }}

See also

Source de la révision

<h2 id="R.C3.A9sum.C3.A9">Résumé</h2>
<p>L'objet global <code>Array</code> est un constructeur de tableaux, qui correspondent à des objets de haut niveau s'apparentant aux listes.</p>
<h2 id="Syntaxe">Syntaxe</h2>
<pre class="syntaxbox">
[<var>element0</var>, <var>element1</var>, ..., <var>elementN</var>]
new Array(<em>element0</em>, <em>element1</em>, ..., <em>elementN</em>)
new Array(<em>arrayLength</em>)
</pre>
<dl>
 <dt>
  <code><var>element0</var>, <var>element1</var>, ..., <var>elementN</var> </code></dt>
 <dd>
  Un tableau en javascript est initialisé avec les éléments passés en paramètre, à l'exception du cas où un seul argument est passé au constructeur de l'objet <code>Array</code> et que cet argument est un chiffre. (Voi ci-dessous.) A noter que ce cas particulié s'applique aux tableaux créent avec le constructeur de l'objet<code> Array</code> , non pas aux tableaux litérales créent avec la syntaxe des crochets.</dd>
 <dt>
  <code><var>arrayLength</var></code></dt>
 <dd>
  Si le seul argument passé au constructeur de l'objet <code>Array</code>&nbsp; est un entier entre 0 et 2<sup>32</sup>-1 (inclus), un nouveau tableau vide est retourné avec sa taille défini par cet entier et contenant autant d'entrées, chacune étant initialisée à <code>undefined</code>. Si l'argument est n'importe quel autre nombre, une exception <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/RangeError" title="JavaScript/Reference/Global_Objects/RangeError">RangeError</a></code> est levée.</dd>
</dl>
<h2 id="Description">Description</h2>
<p>Les tableaux sont des objets s'apparentant aux listes qui possèdent plusieurs méthodes de base pour exécuter des opérations de parcours et de mutation. Ni la taille du tableau en Javascript ni le type de ses éléments n'est dixé. Comme la taille d'un tableau peut augmenter ou diminuer à n'importe quel moment, les tableaux en Javascript ne sont pas garantis denses. Globalement, ce sont des charactéristiques utiles; mais si c'est fonctionnalité ne sont pas souhaitable pour votre cas d'utilisation, vous pouvez considérer l'utilisation de tableaux de type WebGL.</p>
<p>Note that <a class="external" href="http://www.andrewdupont.net/2006/05/18/javascript-associative-arrays-considered-harmful/">you shouldn't use an array as an associative array</a>. You can use plain <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Object" title="JavaScript/Reference/Global Objects/Object">objects</a> instead, although doing so comes with its own caveats. See the post <a class="external" href="http://monogatari.doukut.su/2010/12/lightweight-javascript-dictionaries.html" title="http://monogatari.doukut.su/2010/12/lightweight-javascript-dictionaries.html">Lightweight JavaScript dictionaries with arbitrary keys</a> as an example.</p>
<h3 id="Accessing_array_elements">Accessing array elements</h3>
<p>JavaScript arrays are zero-indexed; the first element of an array is actually at index <code>0</code>, and the last element is at the index equal to the value of the array's <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/length" title="JavaScript/Reference/Global_Objects/Array/length"><code>length</code></a> property minus 1.</p>
<pre class="brush: js">
var arr = ["this is the first element", "this is the second element"];
console.log(arr[0]);              // prints "this is the first element"
console.log(arr[1]);              // prints "this is the second element"
console.log(arr[arr.length - 1]); // prints "this is the second element"
</pre>
<p>Array elements are just object properties, in the way that <code><a href="/en-US/docs/toString" title="toString">toString</a></code> is a property. However, note that trying to access the first element of an array as follows will throw a syntax error:</p>
<pre class="brush: js">
console.log(arr.0);
</pre>
<p>Note that there is nothing unique about JavaScript arrays and their properties that causes this. JavaScript properties that begin with a digit cannot be referenced with dot notation. They must be accessed using bracket notation. For example, if you had an object with a property "3d", it too would have to be referenced using bracket notation, not dot notation. This similarity is exhibited in the following two code samples:</p>
<pre class="brush: js">
var years = [1950, 1960, 1970, 1980, 1990, 2000, 2010];
try {
  console.log(years.0);
}
catch (ex) {
  console.log("Using bracket notation");
  console.log(years[0]);
}
</pre>
<pre class="brush: js">
try {
  renderer.3d.setTexture(model, "character.png");
}
catch (ex) {
  console.log("Using bracket notation");
  renderer["3d"].setTexture(model, "character.png");
}
</pre>
<p>Note that in the <code>3d</code> example, "<code>3d</code>" had to be quoted. It's possible to quote the JavaScript array indexes as well (e.g., <code>years["2"]</code> instead of <code>years[2]</code>), although it's not necessary. The 2 in <code>years[2]</code> eventually gets coerced into a string by the JavaScript engine, anyway, through an implicit <code>toString</code> conversion. It is for this reason that "2" and "02" would refer to two different slots on the <code>years</code> object and the following example logs <code>true</code>:</p>
<pre class="brush: js">
console.log(years["2"] != years["02"]);
</pre>
<h3 id="Relationship_between_length_and_numerical_properties">Relationship between <code>length</code> and numerical properties</h3>
<p>A JavaScript array's <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/length" title="JavaScript/Reference/Global_Objects/Array/length">length</a></code> property and numerical properties are connected. Several of the built-in array methods (e.g., <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/join" title="JavaScript/Reference/Global_Objects/Array/join">join</a></code>, <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/slice" title="JavaScript/Reference/Global_Objects/Array/slice">slice</a></code>, <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/indexOf" title="JavaScript/Reference/Global_Objects/Array/indexOf">indexOf</a></code>, etc.) take into account the value of an array's <code>length</code> property when they're called. Other methods (e.g., <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/push" title="JavaScript/Reference/Global_Objects/Array/push">push</a></code>, <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/splice" title="JavaScript/Reference/Global_Objects/Array/splice">splice</a></code>, etc.) also result in updates to an array's <code>length</code> property.</p>
<pre class="brush: js">
var fruits = [];
fruits.push("banana", "apple", "peach");

console.log(fruits.length); // 3</pre>
<p>When setting a property on a JavaScript array when the property is a valid array index and that index is outside the current bounds of the array, the array will grow to a size large enough to accommodate an element at that index, and the engine will update the array's <code>length</code> property accordingly:</p>
<pre class="brush: js">
fruits[3] = "mango";
console.log(fruits[3]);
console.log(fruits.length); // 4</pre>
<p>Setting the <code>length</code> property, directly, also results in special behavior.</p>
<pre class="brush: js">
fruits.length = 10;
console.log(fruits);        // The array gets padded with undefined
console.log(fruits.length); // 10
</pre>
<p>This is explained further on the <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/length" title="JavaScript/Reference/Global_Objects/Array/length"><code>length</code></a> page.</p>
<h3 id="Creating_an_array_using_the_result_of_a_match">Creating an array using the result of a match</h3>
<p>The result of a match between a regular expression and a string can create a JavaScript 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:</p>
<pre class="brush: js">
// 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");
</pre>
<p>The properties and elements returned from this match are as follows:</p>
<table class="fullwidth-table">
 <tbody>
  <tr>
   <td class="header">Property/Element</td>
   <td class="header">Description</td>
   <td class="header">Example</td>
  </tr>
  <tr>
   <td><code>input</code></td>
   <td>A read-only property that reflects the original string against which the regular expression was matched.</td>
   <td>cdbBdbsbz</td>
  </tr>
  <tr>
   <td><code>index</code></td>
   <td>A read-only property that is the zero-based index of the match in the string.</td>
   <td>1</td>
  </tr>
  <tr>
   <td><code>[0]</code></td>
   <td>A read-only element that specifies the last matched characters.</td>
   <td>dbBd</td>
  </tr>
  <tr>
   <td><code>[1], ...[n]</code></td>
   <td>Read-only elements that specify the parenthesized substring matches, if included in the regular expression. The number of possible parenthesized substrings is unlimited.</td>
   <td>[1]: bB<br />
    [2]: d</td>
  </tr>
 </tbody>
</table>
<h2 id="Properties">Properties</h2>
<p>{{ Js_see_prototype("Array", "Properties") }}</p>
<dl>
 <dt>
  <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype" title="JavaScript/Reference/Global_Objects/Array/prototype">prototype</a></dt>
 <dd>
  Allows the addition of properties to all objects.</dd>
</dl>
<div>
 {{ jsOverrides("Function", "Properties", "prototype") }}</div>
<h2 id="Methods">Methods</h2>
<div>
 {{ Js_see_prototype("Array", "Methods") }}</div>
<dl>
 <dt>
  <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/isArray" title="JavaScript/Reference/Global Objects/Array/isArray">isArray</a> {{ js_minversion_inline("1.8.5") }}</dt>
 <dd>
  Return true if a variable is an array, if not false.</dd>
</dl>
<h2 id="Array_instances"><code>Array</code> instances</h2>
<p><code>Array</code> instances inherit from<span style="font-family: monospace;"> <code><a href="/en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype" title="Core_JavaScript_1.5_Reference/Global_Objects/Array/prototype">Array.prototype</a></code></span>. As with all constructors, you can change the constructor's prototype object to make changes to all JavaScript <code>Array</code> instances.</p>
<h3 id="Properties_of_Array_instances" name="Properties_of_Array_instances">Properties</h3>
<div>
 {{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Properties') }}</div>
<h3 id="Methods_of_Array_instances" name="Methods_of_Array_instances">Methods</h3>
<h4 id="Mutator_methods">Mutator methods</h4>
<div>
 {{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Mutator_methods') }}</div>
<h4 id="Accessor_methods"><span>Accessor methods</span></h4>
<div>
 {{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Accessor_methods') }}</div>
<h4 id="Iteration_methods"><span>Iteration methods</span></h4>
<div>
 {{ page('en-US/docs/JavaScript/Reference/Global_Objects/Array/prototype', 'Iteration_methods') }}</div>
<h2 id="Examples">Examples</h2>
<h3 id="Example.3A_Creating_an_array">Example: Creating an array</h3>
<p>The following example creates an array, <code>msgArray</code>, with a length of 0, then assigns values to <code>msgArray[0]</code> and <code>msgArray[99]</code>, changing the length of the array to 100.</p>
<pre class="brush: js">
var msgArray = new Array();
msgArray[0] = "Hello";
msgArray[99] = "world";

if (msgArray.length == 100)
   print("The length is 100.");
</pre>
<h3 id="Example.3A_Creating_a_two-dimensional_array">Example: Creating a two-dimensional array</h3>
<p>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 old position 6,4 is made blank.</p>
<pre class="brush: js">
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'));
</pre>
<p>Here is the output:</p>
<pre class="eval">
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
</pre>
<h2 id="Browser_compatibility" name="Browser_compatibility">Browser compatibility</h2>
<p>{{ CompatibilityTable }}</p>
<div id="compat-desktop">
 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Chrome</th>
    <th>Firefox (Gecko)</th>
    <th>Internet Explorer</th>
    <th>Opera</th>
    <th>Safari (WebKit)</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
   </tr>
  </tbody>
 </table>
</div>
<div id="compat-mobile">
 <table class="compat-table">
  <tbody>
   <tr>
    <th>Feature</th>
    <th>Android</th>
    <th>Firefox Mobile (Gecko)</th>
    <th>IE Phone</th>
    <th>Opera Mobile</th>
    <th>Safari Mobile</th>
   </tr>
   <tr>
    <td>Basic support</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
    <td>{{ CompatVersionUnknown }}</td>
   </tr>
  </tbody>
 </table>
</div>
<h2 id="See_also" name="See_also">See also</h2>
<ul>
 <li><a href="/en-US/docs/JavaScript/Guide/Working_with_Objects#Indexing_object_properties" title="JavaScript/Guide/Working_with_objects#Indexing_object_properties">"Indexing object properties" in JavaScript Guide: "Working with objects"</a></li>
 <li><a href="/en-US/docs/JavaScript/New_in_JavaScript/1.7#Array_comprehensions" title="New_in_JavaScript_1.7#Array_comprehensions">New in JavaScript 1.7: Array comprehensions</a></li>
 <li><a href="/en-US/docs/JavaScript/New_in_JavaScript/1.6#Array_extras" title="New_in_JavaScript_1.6#Array_extras">New in JavaScript 1.6: Array extras</a></li>
 <li><a href="/en-US/docs/JavaScript_typed_arrays" title="JavaScript_typed_arrays">Draft: Typed Arrays</a></li>
</ul>
<!-- languages({
  "fr": "fr/JavaScript/R%C3%A9f%C3%A9rence_JavaScript/Objets_globaux/Array",
})-->
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