Revision 695593 of while

<div>
 <div>
  {{jsSidebar("Statements")}}</div>
</div>
<h2 id="Summary" name="Summary">Summary</h2>
<p>The <strong>while statement</strong> creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.</p>
<h2 id="Syntax" name="Syntax">Syntax</h2>
<pre class="syntaxbox">
while (<em>condition</em>) {
  <em>statement</em>
}</pre>
<dl>
 <dt>
  <code>condition</code></dt>
 <dd>
  An expression evaluated before each pass through the loop. If this condition evaluates to true, <code>statement</code> is executed. When condition evaluates to false, execution continues with the statement after the <code>while</code> loop.</dd>
 <dt>
  <code>statement</code></dt>
 <dd>
  A statement that is executed as long as the condition evaluates to true. To execute multiple statements within the loop, use a <a href="/en-US/docs/JavaScript/Reference/Statements/block" title="JavaScript/Reference/Statements/block">block</a> statement (<code>{ ... }</code>) to group those statements.</dd>
</dl>
<h2 id="Examples" name="Examples">Examples</h2>
<p>The following <code>while</code> loop iterates as long as <code>n</code> is less than three.</p>
<pre class="brush:js">
var n = 0;
var x = 0;

while (n &lt; 3) {
  n++;
  x += n;
}</pre>
<p>Each iteration, the loop increments <code>n</code> and adds it to <code>x</code>. Therefore, <code>x</code> and <code>n</code> take on the following values:</p>
<ul>
 <li>After the first pass: <code>n</code> = 1 and <code>x</code> = 1</li>
 <li>After the second pass: <code>n</code> = 2 and <code>x</code> = 3</li>
 <li>After the third pass: <code>n</code> = 3 and <code>x</code> = 6</li>
</ul>
<p>After completing the third pass, the condition <code>n</code> &lt; 3 is no longer true, so the loop terminates.</p>
<h2 id="Specifications">Specifications</h2>
<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>ECMAScript 1st Edition.</td>
   <td>Standard</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ES5.1', '#sec-12.6.2', 'while statement')}}</td>
   <td>{{Spec2('ES5.1')}}</td>
   <td>&nbsp;</td>
  </tr>
  <tr>
   <td>{{SpecName('ES6', '#sec-while-statement', 'while statement')}}</td>
   <td>{{Spec2('ES6')}}</td>
   <td>&nbsp;</td>
  </tr>
 </tbody>
</table>
<h2 id="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</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>Chrome for Android</th>
    <th>Firefox Mobile (Gecko)</th>
    <th>IE Mobile</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>
    <td>{{ CompatVersionUnknown() }}</td>
   </tr>
  </tbody>
 </table>
</div>
<h2 id="See_also" name="See_also">See also</h2>
<ul>
 <li><a href="/en-US/docs/Web/JavaScript/Reference/Statements/do...while"><code>do...while</code></a></li>
 <li>{{jsxref("Statements/for", "for")}}</li>
</ul>
<!--languages( { "fr": "fr/R\u00e9f\u00e9rence_de_JavaScript_1.5_Core/Instructions/while" } )-->