path: root/files/zh-cn/web/api/windoworworkerglobalscope/setinterval/index.html

---
title: window.setInterval
slug: Web/API/Window/setInterval
tags:
  - API
  - DOM
  - 定时
  - 方法
  - 时间
translation_of: Web/API/WindowOrWorkerGlobalScope/setInterval
---
<div>{{ ApiRef("HTML DOM") }}</div>

<p>{{domxref("WindowOrWorkerGlobalScope")}} 的 <strong><code>setInterval()</code> </strong>方法重复调用一个函数或执行一个代码段，在每次调用之间具有固定的时间延迟。</p>

<p><span class="seoSummary">在窗口和工作接口上提供的<strong>setInterval()</strong>方法重复调用函数或执行代码片段，每次调用之间有固定的时间延迟。它返回一个时间间隔ID，该ID唯一地标识时间间隔，因此您可以稍后通过调用<strong>clearInterval()</strong>来删除它。这个方法是由<strong>WindowOrWorkerGlobalScope mixin</strong>定义的。</span></p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox notranslate"><em>var intervalID</em> = scope.setInterval(<em>func</em>, <em>delay</em>, [<em>arg1</em>, <em>arg2</em>, ...]);
<em>var intervalID</em> = scope.setInterval(<em>code</em>, <em>delay</em>);
</pre>

<h3 id="参数">参数</h3>

<dl>
 <dt><code>func</code></dt>
 <dd>要重复调用的函数。 每经过指定 <code>延迟</code> 毫秒后执行的{{jsxref("函数")}} 。该函数不接受任何参数，也没有返回值。</dd>
 <dt><code>code</code></dt>
 <dd>这个语法是可选的，你可以传递一个字符串来代替一个函数对象，你传递的字符串会被编译然后每个delay毫秒时间内执行一次。这个语法因为存在安全风险所以不被推荐使用。</dd>
 <dt><code>delay</code></dt>
 <dd>是每次延迟的毫秒数 (一秒等于1000毫秒)，函数的每次调用会在该延迟之后发生。和<a href="/en-US/docs/DOM/window.setTimeout#Minimum_delay_and_timeout_nesting" title="en-US/docs/DOM/window.setTimeout#Minimum delay and timeout nesting">setTimeout</a>一样，实际的延迟时间可能会稍长一点。这个时间计算单位是毫秒（千分之一秒），这个定时器会使指定方法或者代码段执行的时候进行时间延迟。如果这个参数值小于10，则默认使用值为10。请注意，真正延迟时间或许更长； 请参考示例： {{SectionOnPage("/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setTimeout", "Reasons for delays longer than specified")}} </dd>
 <dt><code>arg1, ..., argN</code> {{optional_inline}}</dt>
 <dd>当定时器过期的时候，将被传递给func指定函数的附加参数。</dd>
</dl>

<h3 id="返回值">返回值</h3>

<p>此返回值<code>intervalID</code>是一个非零数值，用来标识通过<code>setInterval()</code>创建的计时器，这个值可以用来作为<code>clearInterval()</code>的参数来清除对应的计时器 。</p>

<p>值得注意的是，<code>setInterval()</code>和<code>setTimeout()</code>共享同一个ID池，并且<code>clearInterval()</code>和<code>clearTimeout()</code>在技术上是可互换使用的。但是，我们必须去匹配<code>clearInterval()</code>和<code>clearTimeout()</code>对应的<code>id，以</code>避免代码杂乱无章，增强代码的可维护性。</p>

<div class="note"><strong>Note</strong>: The <code>delay</code> argument is converted to a signed 32-bit integer. This effectively limits <code>delay</code> to 2147483647 ms, since it's specified as a signed integer in the IDL.</div>

<h2 id="示例">示例</h2>

<h3 id="例１：基本用法">例１：基本用法</h3>

<p>下面例子是 <code>setInterval()</code>的基本语法</p>

<pre class="brush:js notranslate">var intervalID = window.setInterval(myCallback, 500, 'Parameter 1', 'Parameter 2');

function myCallback(a, b)
{
 // Your code here
 // Parameters are purely optional.
 console.log(a);
 console.log(b);
}
</pre>

<h3 id="例２：两种颜色的切换">例２：两种颜色的切换</h3>

<p>下面的例子里会每隔一秒就调用函数 <code>flashtext()</code> 一次，直至你通过按下 Stop 按钮来清除本次重复操作的唯一辨识符 <code>intervalID</code>。</p>

<pre class="brush:html notranslate">&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
  &lt;meta charset="UTF-8" /&gt;
  &lt;title&gt;setInterval/clearInterval example&lt;/title&gt;

  &lt;script&gt;
    var nIntervId;

    function changeColor() {
      nIntervId = setInterval(flashText, 1000);
    }

    function flashText() {
      var oElem = document.getElementById('my_box');
      oElem.style.color = oElem.style.color == 'red' ? 'blue' : 'red';
      // oElem.style.color == 'red' ? 'blue' : 'red' is a ternary operator.
    }

    function stopTextColor() {
      clearInterval(nIntervId);
    }
  &lt;/script&gt;
&lt;/head&gt;

&lt;body onload="changeColor();"&gt;
  &lt;div id="my_box"&gt;
    &lt;p&gt;Hello World&lt;/p&gt;
  &lt;/div&gt;

  &lt;button onclick="stopTextColor();"&gt;Stop&lt;/button&gt;
&lt;/body&gt;
&lt;/html&gt;
</pre>

<h3 id="例３：打字机效果">例３：打字机效果</h3>

<p>下面这个例子通过键入、删除和再次键入所有 <a href="/en-US/docs/DOM/NodeList"><code>NodeList</code></a> 中的符合特定的选择器的字符，以达到打字机的效果。</p>

<div>
<pre class="brush:html notranslate">&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
&lt;meta charset="UTF-8" /&gt;
&lt;title&gt;JavaScript Typewriter - MDN Example&lt;/title&gt;
&lt;script&gt;
function Typewriter (sSelector, nRate) {

  function clean () {
    clearInterval(nIntervId);
    bTyping = false;
    bStart = true;
    oCurrent = null;
    aSheets.length = nIdx = 0;
  }

  function scroll (oSheet, nPos, bEraseAndStop) {
    if (!oSheet.hasOwnProperty("parts") || aMap.length &lt; nPos) { return true; }

    var oRel, bExit = false;

    if (aMap.length === nPos) { aMap.push(0); }

    while (aMap[nPos] &lt; oSheet.parts.length) {
      oRel = oSheet.parts[aMap[nPos]];

      scroll(oRel, nPos + 1, bEraseAndStop) ? aMap[nPos]++ : bExit = true;

      if (bEraseAndStop &amp;&amp; (oRel.ref.nodeType - 1 | 1) === 3 &amp;&amp; oRel.ref.nodeValue) {
        bExit = true;
        oCurrent = oRel.ref;
        sPart = oCurrent.nodeValue;
        oCurrent.nodeValue = "";
      }

      oSheet.ref.appendChild(oRel.ref);
      if (bExit) { return false; }
    }

    aMap.length--;
    return true;
  }

  function typewrite () {
    if (sPart.length === 0 &amp;&amp; scroll(aSheets[nIdx], 0, true) &amp;&amp; nIdx++ === aSheets.length - 1) { clean(); return; }

    oCurrent.nodeValue += sPart.charAt(0);
    sPart = sPart.slice(1);
  }

  function Sheet (oNode) {
    this.ref = oNode;
    if (!oNode.hasChildNodes()) { return; }
    this.parts = Array.prototype.slice.call(oNode.childNodes);

    for (var nChild = 0; nChild &lt; this.parts.length; nChild++) {
      oNode.removeChild(this.parts[nChild]);
      this.parts[nChild] = new Sheet(this.parts[nChild]);
    }
  }

  var
    nIntervId, oCurrent = null, bTyping = false, bStart = true,
    nIdx = 0, sPart = "", aSheets = [], aMap = [];

  this.rate = nRate || 100;

  this.play = function () {
    if (bTyping) { return; }
    if (bStart) {
      var aItems = document.querySelectorAll(sSelector);

      if (aItems.length === 0) { return; }
      for (var nItem = 0; nItem &lt; aItems.length; nItem++) {
        aSheets.push(new Sheet(aItems[nItem]));
        /* Uncomment the following line if you have previously hidden your elements via CSS: */
        // aItems[nItem].style.visibility = "visible";
      }

      bStart = false;
    }

    nIntervId = setInterval(typewrite, this.rate);
    bTyping = true;
  };

  this.pause = function () {
    clearInterval(nIntervId);
    bTyping = false;
  };

  this.terminate = function () {
    oCurrent.nodeValue += sPart;
    sPart = "";
    for (nIdx; nIdx &lt; aSheets.length; scroll(aSheets[nIdx++], 0, false));
    clean();
  };
}

/* usage: */
var oTWExample1 = new Typewriter(/* elements: */ "#article, h1, #info, #copyleft", /* frame rate (optional): */ 15);

/* default frame rate is 100: */
var oTWExample2 = new Typewriter("#controls");

/* you can also change the frame rate value modifying the "rate" property; for example: */
// oTWExample2.rate = 150;

onload = function () {
  oTWExample1.play();
  oTWExample2.play();
};
&lt;/script&gt;
&lt;style type="text/css"&gt;
span.intLink, a, a:visited {
  cursor: pointer;
  color: #000000;
  text-decoration: underline;
}

#info {
  width: 180px;
  height: 150px;
  float: right;
  background-color: #eeeeff;
  padding: 4px;
  overflow: auto;
  font-size: 12px;
  margin: 4px;
  border-radius: 5px;
  /* visibility: hidden; */
}
&lt;/style&gt;
&lt;/head&gt;

&lt;body&gt;

&lt;p id="copyleft" style="font-style: italic; font-size: 12px; text-align: center;"&gt;CopyLeft 2012 by &lt;a href="https://developer.mozilla.org/" target="_blank"&gt;Mozilla Developer Network&lt;/a&gt;&lt;/p&gt;
&lt;p id="controls" style="text-align: center;"&gt;[&amp;nbsp;&lt;span class="intLink" onclick="oTWExample1.play();"&gt;Play&lt;/span&gt; | &lt;span class="intLink" onclick="oTWExample1.pause();"&gt;Pause&lt;/span&gt; | &lt;span class="intLink" onclick="oTWExample1.terminate();"&gt;Terminate&lt;/span&gt;&amp;nbsp;]&lt;/p&gt;
&lt;div id="info"&gt;
Vivamus blandit massa ut metus mattis in fringilla lectus imperdiet. Proin ac ante a felis ornare vehicula. Fusce pellentesque lacus vitae eros convallis ut mollis magna pellentesque. Pellentesque placerat enim at lacus ultricies vitae facilisis nisi fringilla. In tincidunt tincidunt tincidunt.
&lt;/div&gt;
&lt;h1&gt;JavaScript Typewriter&lt;/h1&gt;

&lt;div id="article"&gt;
&lt;p&gt;Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam ultrices dolor ac dolor imperdiet ullamcorper. Suspendisse quam libero, luctus auctor mollis sed, malesuada condimentum magna. Quisque in ante tellus, in placerat est. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Donec a mi magna, quis mattis dolor. Etiam sit amet ligula quis urna auctor imperdiet nec faucibus ante. Mauris vel consectetur dolor. Nunc eget elit eget velit pulvinar fringilla consectetur aliquam purus. Curabitur convallis, justo posuere porta egestas, velit erat ornare tortor, non viverra justo diam eget arcu. Phasellus adipiscing fermentum nibh ac commodo. Nam turpis nunc, suscipit a hendrerit vitae, volutpat non ipsum.&lt;/p&gt;
&lt;form&gt;
&lt;p&gt;Phasellus ac nisl lorem: &lt;input type="text" /&gt;&lt;br /&gt;
&lt;textarea style="width: 400px; height: 200px;"&gt;Nullam commodo suscipit lacus non aliquet. Phasellus ac nisl lorem, sed facilisis ligula. Nam cursus lobortis placerat. Sed dui nisi, elementum eu sodales ac, placerat sit amet mauris. Pellentesque dapibus tellus ut ipsum aliquam eu auctor dui vehicula. Quisque ultrices laoreet erat, at ultrices tortor sodales non. Sed venenatis luctus magna, ultricies ultricies nunc fringilla eget. Praesent scelerisque urna vitae nibh tristique varius consequat neque luctus. Integer ornare, erat a porta tempus, velit justo fermentum elit, a fermentum metus nisi eu ipsum. Vivamus eget augue vel dui viverra adipiscing congue ut massa. Praesent vitae eros erat, pulvinar laoreet magna. Maecenas vestibulum mollis nunc in posuere. Pellentesque sit amet metus a turpis lobortis tempor eu vel tortor. Cras sodales eleifend interdum.&lt;/textarea&gt;&lt;/p&gt;
&lt;input type="submit" value="Send" /&gt;
&lt;/form&gt;
&lt;p&gt;Duis lobortis sapien quis nisl luctus porttitor. In tempor semper libero, eu tincidunt dolor eleifend sit amet. Ut nec velit in dolor tincidunt rhoncus non non diam. Morbi auctor ornare orci, non euismod felis gravida nec. Curabitur elementum nisi a eros rutrum nec blandit diam placerat. Aenean tincidunt risus ut nisi consectetur cursus. Ut vitae quam elit. Donec dignissim est in quam tempor consequat. Aliquam aliquam diam non felis convallis suscipit. Nulla facilisi. Donec lacus risus, dignissim et fringilla et, egestas vel eros. Duis malesuada accumsan dui, at fringilla mauris bibStartum quis. Cras adipiscing ultricies fermentum. Praesent bibStartum condimentum feugiat.&lt;/p&gt;
&lt;p&gt;Nam faucibus, ligula eu fringilla pulvinar, lectus tellus iaculis nunc, vitae scelerisque metus leo non metus. Proin mattis lobortis lobortis. Quisque accumsan faucibus erat, vel varius tortor ultricies ac. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed nec libero nunc. Nullam tortor nunc, elementum a consectetur et, ultrices eu orci. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Pellentesque a nisl eu sem vehicula egestas.&lt;/p&gt;
&lt;/div&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>
</div>

<p><a href="/files/3997/typewriter.html">查看示例效果</a>，亦可参考：<a href="https://developer.mozilla.org/zh-CN/docs/DOM/window.clearInterval" title="en-US/docs/DOM/window.clearInterval"><code>clearInterval()</code></a>。</p>

<h2 id="回调参数">回调参数</h2>

<p>如前所述，Internet Explorer 9及以下版本不支持在<code>setTimeout()</code>或<code>setInterval()</code>中向回调函数传递参数。下面的IE专用代码演示了一种克服这种限制的方法。使用时，只需将以下代码添加到你的脚本顶部即可。</p>

<pre class="brush:js notranslate">/*\
|*|
|*|  IE-specific polyfill that enables the passage of arbitrary arguments to the
|*|  callback functions of javascript timers (HTML5 standard syntax).
|*|
|*|  https://developer.mozilla.org/en-US/docs/Web/API/window.setInterval
|*|  https://developer.mozilla.org/User:fusionchess
|*|
|*|  Syntax:
|*|  var timeoutID = window.setTimeout(func, delay[, arg1, arg2, ...]);
|*|  var timeoutID = window.setTimeout(code, delay);
|*|  var intervalID = window.setInterval(func, delay[, arg1, arg2, ...]);
|*|  var intervalID = window.setInterval(code, delay);
|*|
\*/

if (document.all &amp;&amp; !window.setTimeout.isPolyfill) {
  var __nativeST__ = window.setTimeout;
  window.setTimeout = function (vCallback, nDelay /*, argumentToPass1, argumentToPass2, etc. */) {
    var aArgs = Array.prototype.slice.call(arguments, 2);
    return __nativeST__(vCallback instanceof Function ? function () {
      vCallback.apply(null, aArgs);
    } : vCallback, nDelay);
  };
  window.setTimeout.isPolyfill = true;
}

if (document.all &amp;&amp; !window.setInterval.isPolyfill) {
  var __nativeSI__ = window.setInterval;
  window.setInterval = function (vCallback, nDelay /*, argumentToPass1, argumentToPass2, etc. */) {
    var aArgs = Array.prototype.slice.call(arguments, 2);
    return __nativeSI__(vCallback instanceof Function ? function () {
      vCallback.apply(null, aArgs);
    } : vCallback, nDelay);
  };
  window.setInterval.isPolyfill = true;
}
</pre>

<p>另一种方式是使用匿名函数调用你的回调函数，但是这种方式开销较大。例如：</p>

<pre class="brush:js notranslate">var intervalID = setInterval(function() { myFunc('one', 'two', 'three'); }, 1000);</pre>

<p>还有一种方式是使用 <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Function/bind" title="/en-US/docs/JavaScript/Reference/Global_Objects/Function/bind">function's bind</a>. 例如：</p>

<pre class="brush:js notranslate">var intervalID = setInterval(function(arg1) {}.bind(undefined, 10), 1000);</pre>

<p>{{h3_gecko_minversion("Inactive tabs", "5.0")}}</p>

<p>Starting in Gecko 5.0 {{geckoRelease("5.0")}}, intervals are clamped to fire no more often than once per second in inactive tabs.</p>

<h2 id="this_的问题">"<a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a>" 的问题</h2>

<p>当你给 <code>setInterval()</code> 传递一个方法或者函数的时候，<a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> 值的绑定会存在一些问题。  这个问题在<a href="/en-US/docs/Web/JavaScript/Reference/Operators/this#As_an_object_method">JavaScript 参考</a> 进行了详细解释。</p>

<h3 id="解释">解释</h3>

<p>Code executed by <code>setInterval()</code> runs in a separate execution context than the function from which it was called. As a consequence, the <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> keyword for the called function is set to the <code>window</code> (or <code>global</code>) object, it is not the same as the <code>this</code> value for the function that called <code>setTimeout</code>. See the following example (which uses <code>setTimeout()</code> instead of <code>setInterval()</code> – the problem, in fact, is the same for both timers):</p>

<pre class="brush:js notranslate">myArray = ['zero', 'one', 'two'];

myArray.myMethod = function (sProperty) {
    alert(arguments.length &gt; 0 ? this[sProperty] : this);
};

myArray.myMethod(); // prints "zero,one,two"
myArray.myMethod(1); // prints "one"
setTimeout(myArray.myMethod, 1000); // prints "[object Window]" after 1 second
setTimeout(myArray.myMethod, 1500, "1"); // prints "undefined" after 1,5 seconds
// passing the 'this' object with .call won't work
// because this will change the value of this inside setTimeout itself
// while we want to change the value of this inside myArray.myMethod
// in fact, it will be an error because setTimeout code expects this to be the window object:
setTimeout.call(myArray, myArray.myMethod, 2000); // error: "NS_ERROR_XPC_BAD_OP_ON_WN_PROTO: Illegal operation on WrappedNative prototype object"
setTimeout.call(myArray, myArray.myMethod, 2500, 2); // same error
</pre>

<p>As you can see there are no ways to pass the <code>this</code> object to the callback function in the legacy JavaScript.</p>

<h3 id="一个可能的解决方案">一个可能的解决方案</h3>

<p>A possible way to solve the "<code>this</code>" problem is to replace the two native <code>setTimeout()</code> or <code>setInterval()</code> global functions with two <em>non-native</em> ones that enable their invocation through the <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Function/call"><code>Function.prototype.call</code></a> method. The following example shows a possible replacement:</p>

<pre class="brush:js notranslate">// Enable the passage of the 'this' object through the JavaScript timers

var __nativeST__ = window.setTimeout, __nativeSI__ = window.setInterval;

window.setTimeout = function (vCallback, nDelay /*, argumentToPass1, argumentToPass2, etc. */) {
  var oThis = this, aArgs = Array.prototype.slice.call(arguments, 2);
  return __nativeST__(vCallback instanceof Function ? function () {
    vCallback.apply(oThis, aArgs);
  } : vCallback, nDelay);
};

window.setInterval = function (vCallback, nDelay /*, argumentToPass1, argumentToPass2, etc. */) {
  var oThis = this, aArgs = Array.prototype.slice.call(arguments, 2);
  return __nativeSI__(vCallback instanceof Function ? function () {
    vCallback.apply(oThis, aArgs);
  } : vCallback, nDelay);
};</pre>

<div class="note">These two replacements also enable the HTML5 standard passage of arbitrary arguments to the callback functions of timers in IE. So they can be used as <em>non-standard-compliant</em> polyfills also. See the <a href="#Callback_arguments">callback arguments paragraph</a> for a <em>standard-compliant</em> polyfill.</div>

<p>New feature test:</p>

<pre class="brush:js notranslate">myArray = ['zero', 'one', 'two'];

myArray.myMethod = function (sProperty) {
    alert(arguments.length &gt; 0 ? this[sProperty] : this);
};

setTimeout(alert, 1500, 'Hello world!'); // the standard use of setTimeout and setInterval is preserved, but...
setTimeout.call(myArray, myArray.myMethod, 2000); // prints "zero,one,two" after 2 seconds
setTimeout.call(myArray, myArray.myMethod, 2500, 2); // prints "two" after 2,5 seconds
</pre>

<p>Another, more complex, solution for<strong> </strong>the <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> problem<strong> </strong>is <a href="#MiniDaemon_-_A_framework_for_managing_timers">the following framework</a>.</p>

<div class="note">JavaScript 1.8.5 introduces the <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind">Function.prototype.bind()</a></code> method, which lets you specify the value that should be used as <code>this</code> for all calls to a given function. This lets you easily bypass problems where it's unclear what this will be, depending on the context from which your function was called. Also, ES2015 supports <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions">arrow functions</a>, with lexical this allowing us to write setInterval( () =&gt; this.myMethod) if we're inside myArray method.</div>

<h2 id="MiniDaemon：一个用于管理定时器的小框架">MiniDaemon：一个用于管理定时器的小框架</h2>

<p>In pages requiring many timers, it can often be difficult to keep track of all of the running timer events. One approach to solving this problem is to store information about the state of a timer in an object. Following is a minimal example of such an abstraction. The constructor architecture explicitly avoids the use of closures. It also offers an alternative way to pass the <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> object to the callback function (see <a href="#The_.22this.22_problem">The "this" problem</a> for details). The following code is also <a href="https://github.com/madmurphy/minidaemon.js">available on GitHub</a>.</p>

<div class="note">For a more complex but still modular version of it (<code><em>Daemon</em></code>) see <a href="/en-US/Add-ons/Code_snippets/Timers/Daemons">JavaScript Daemons Management</a>. This more complex version is nothing but a big and scalable collection of methods for the <code><em>Daemon</em></code> constructor. However, the <code><em>Daemon</em></code> constructor itself is nothing but a clone of <code><em>MiniDaemon</em></code> with an added support for <em>init</em> and <em>onstart</em> functions declarable during the instantiation of the <code><em>daemon</em></code>. <strong>So the <code><em>MiniDaemon</em></code> framework remains the recommended way for simple animations</strong>, because <code><em>Daemon</em></code> without its collection of methods is essentially a clone of it.</div>

<h3 id="minidaemon.js">minidaemon.js</h3>

<div>
<pre class="brush:js notranslate">/*\
|*|
|*|  :: MiniDaemon ::
|*|
|*|  Revision #2 - September 26, 2014
|*|
|*|  https://developer.mozilla.org/en-US/docs/Web/API/window.setInterval
|*|  https://developer.mozilla.org/User:fusionchess
|*|  https://github.com/madmurphy/minidaemon.js
|*|
|*|  This framework is released under the GNU Lesser General Public License, version 3 or later.
|*|  http://www.gnu.org/licenses/lgpl-3.0.html
|*|
\*/

function MiniDaemon (oOwner, fTask, nRate, nLen) {
  if (!(this &amp;&amp; this instanceof MiniDaemon)) { return; }
  if (arguments.length &lt; 2) { throw new TypeError('MiniDaemon - not enough arguments'); }
  if (oOwner) { this.owner = oOwner; }
  this.task = fTask;
  if (isFinite(nRate) &amp;&amp; nRate &gt; 0) { this.rate = Math.floor(nRate); }
  if (nLen &gt; 0) { this.length = Math.floor(nLen); }
}

MiniDaemon.prototype.owner = null;
MiniDaemon.prototype.task = null;
MiniDaemon.prototype.rate = 100;
MiniDaemon.prototype.length = Infinity;

  /* These properties should be read-only */

MiniDaemon.prototype.SESSION = -1;
MiniDaemon.prototype.INDEX = 0;
MiniDaemon.prototype.PAUSED = true;
MiniDaemon.prototype.BACKW = true;

  /* Global methods */

MiniDaemon.forceCall = function (oDmn) {
  oDmn.INDEX += oDmn.BACKW ? -1 : 1;
  if (oDmn.task.call(oDmn.owner, oDmn.INDEX, oDmn.length, oDmn.BACKW) === false || oDmn.isAtEnd()) { oDmn.pause(); return false; }
  return true;
};

  /* Instances methods */

MiniDaemon.prototype.isAtEnd = function () {
  return this.BACKW ? isFinite(this.length) &amp;&amp; this.INDEX &lt; 1 : this.INDEX + 1 &gt; this.length;
};

MiniDaemon.prototype.synchronize = function () {
  if (this.PAUSED) { return; }
  clearInterval(this.SESSION);
  this.SESSION = setInterval(MiniDaemon.forceCall, this.rate, this);
};

MiniDaemon.prototype.pause = function () {
  clearInterval(this.SESSION);
  this.PAUSED = true;
};

MiniDaemon.prototype.start = function (bReverse) {
  var bBackw = Boolean(bReverse);
  if (this.BACKW === bBackw &amp;&amp; (this.isAtEnd() || !this.PAUSED)) { return; }
  this.BACKW = bBackw;
  this.PAUSED = false;
  this.synchronize();
};
</pre>
</div>

<div class="note">MiniDaemon passes arguments to the callback function. If you want to work on it with browsers that natively do not support this feature, use one of the methods proposed above.</div>

<h3 id="语法_2">语法</h3>

<p><code>var myDaemon = new MiniDaemon(<em>thisObject</em>, <em>callback</em>[</code><code>, <em>rate</em></code><code>[, <em>length</em>]]);</code></p>

<h3 id="说明">说明</h3>

<p>Returns a JavaScript <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object"><code>Object</code></a> containing all information needed by an animation (like the <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> object, the callback function, the length, the frame-rate).</p>

<h4 id="参数_2">参数</h4>

<dl>
 <dt><code>thisObject</code></dt>
 <dd>The <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> object on which the <em>callback</em> function is called. It can be an <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object"><code>object</code></a> or <code>null</code>.</dd>
 <dt><code>callback</code></dt>
 <dd>The function that is repeatedly invoked . <strong>It is called with three arguments</strong>: <em>index</em> (the iterative index of each invocation), <em>length</em> (the number of total invocations assigned to the <em>daemon</em> - finite or <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Infinity"><code>Infinity</code></a>) and <em>backwards</em> (a boolean expressing whether the <em>index</em> is increasing or decreasing). It is something like <em>callback</em>.call(<em>thisObject</em>, <em>index</em>, <em>length</em>, <em>backwards</em>). <strong>If the callback function returns a <code>false</code> value the <em>daemon</em> is paused</strong>.</dd>
 <dt><code>rate (optional)</code></dt>
 <dd>The time lapse (in number of milliseconds) between each invocation. The default value is 100.</dd>
 <dt><code>length (optional)</code></dt>
 <dd>The total number of invocations. It can be a positive integer or <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity"><code>Infinity</code></a>. The default value is <code>Infinity</code>.</dd>
</dl>

<h4 id="MiniDaemon_实例（instance）的属性"><code>MiniDaemon</code> 实例（instance）的属性</h4>

<dl>
 <dt><code>myDaemon.owner</code></dt>
 <dd>The <a href="/en-US/docs/Web/JavaScript/Reference/Operators/this"><code>this</code></a> object on which is executed the daemon (read/write). It can be an <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object"><code>object</code></a> or <code>null</code>.</dd>
 <dt><code>myDaemon.task</code></dt>
 <dd>The function that is repeatedly invoked (read/write). It is called with three arguments: <em>index</em> (the iterative index of each invocation), <em>length</em> (the number of total invocations assigned to the daemon - finite or <a href="/en-US/docs/JavaScript/Reference/Global_Objects/Infinity"><code>Infinity</code></a>) and backwards (a boolean expressing whether the <em>index</em> is decreasing or not) – see above. If the <code>myDaemon.task</code> function returns a <code>false</code> value the <em>daemon</em> is paused.</dd>
 <dt><code>myDaemon.rate</code></dt>
 <dd>The time lapse (in number of milliseconds) between each invocation (read/write).</dd>
 <dt><code>myDaemon.length</code></dt>
 <dd>The total number of invocations. It can be a positive integer or <a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Infinity"><code>Infinity</code></a> (read/write).</dd>
</dl>

<h4 id="MiniDaemon_实例的方法"><code>MiniDaemon</code> 实例的方法</h4>

<dl>
 <dt><code>myDaemon.isAtEnd()</code></dt>
 <dd>Returns a boolean expressing whether the <em>daemon</em> is at the start/end position or not.</dd>
 <dt><code>myDaemon.synchronize()</code></dt>
 <dd>Synchronize the timer of a started daemon with the time of its invocation.</dd>
 <dt><code>myDaemon.pause()</code></dt>
 <dd>Pauses the daemon.</dd>
 <dt><code>myDaemon.start([<em>reverse</em>])</code></dt>
 <dd>Starts the daemon forward (<em>index</em> of each invocation increasing) or backwards (<em>index</em> decreasing).</dd>
</dl>

<h4 id="MiniDaemon_全局对象的方法"><code>MiniDaemon</code> 全局对象的方法</h4>

<dl>
 <dt><code>MiniDaemon.forceCall(<em>minidaemon</em>)</code></dt>
 <dd>Forces a single callback to the <code><em>minidaemon</em>.task</code> function regardless of the fact that the end has been reached or not. In any case the internal <code>INDEX</code> property is increased/decreased (depending on the actual direction of the process).</dd>
</dl>

<h3 id="使用示例">使用示例</h3>

<p>HTML：</p>

<pre class="brush:html notranslate">&lt;!DOCTYPE html&gt;
&lt;html&gt;
&lt;head&gt;
  &lt;meta charset="UTF-8" /&gt;
  &lt;title&gt;MiniDaemin Example - MDN&lt;/title&gt;
  &lt;script type="text/javascript" src="minidaemon.js"&gt;&lt;/script&gt;
  &lt;style type="text/css"&gt;
    #sample_div {
      visibility: hidden;
    }
  &lt;/style&gt;
&lt;/head&gt;

&lt;body&gt;
  &lt;p&gt;
    &lt;input type="button" onclick="fadeInOut.start(false /* optional */);" value="fade in" /&gt;
    &lt;input type="button" onclick="fadeInOut.start(true);" value="fade out"&gt;
    &lt;input type="button" onclick="fadeInOut.pause();" value="pause" /&gt;
  &lt;/p&gt;

  &lt;div id="sample_div"&gt;Some text here&lt;/div&gt;

  &lt;script type="text/javascript"&gt;
    function opacity (nIndex, nLength, bBackwards) {
      this.style.opacity = nIndex / nLength;
      if (bBackwards ? nIndex === 0 : nIndex === 1) {
        this.style.visibility = bBackwards ? 'hidden' : 'visible';
      }
    }

    var fadeInOut = new MiniDaemon(document.getElementById('sample_div'), opacity, 300, 8);
  &lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;</pre>

<p><a href="/files/3995/minidaemon_example.html" title="MiniDaemon Example">View this example in action</a></p>

<h2 id="备注">备注</h2>

<p>The <code>setInterval()</code> function is commonly used to set a delay for functions that are executed again and again, such as animations.</p>

<p>You can cancel the interval using {{domxref("WindowOrWorkerGlobalScope.clearInterval()")}}.</p>

<p>If you wish to have your function called <em>once</em> after the specified delay, use {{domxref("WindowOrWorkerGlobalScope.setTimeout()")}}.</p>

<h3 id="Ensure_that_execution_duration_is_shorter_than_interval_frequency">Ensure that execution duration is shorter than interval frequency</h3>

<p>If there is a possibility that your logic could take longer to execute than the interval time, it is recommended that you recursively call a named function using {{domxref("WindowOrWorkerGlobalScope.setTimeout")}}. For example, if using <code>setInterval</code> to poll a remote server every 5 seconds, network latency, an unresponsive server, and a host of other issues could prevent the request from completing in its allotted time. As such, you may find yourself with queued up XHR requests that won't necessarily return in order.</p>

<p>In these cases, a recursive <code>setTimeout()</code> pattern is preferred:</p>

<pre class="brush:js notranslate">(function loop(){
   setTimeout(function() {
      // Your logic here

      loop();
  }, delay);
})();
</pre>

<p>In the above snippet, a named function <code>loop()</code> is declared and is immediately executed. <code>loop()</code> is recursively called inside <code>setTimeout()</code> after the logic has completed executing. While this pattern does not guarantee execution on a fixed interval, it does guarantee that the previous interval has completed before recursing.</p>

<h3 id="Throttling_of_intervals">Throttling of intervals</h3>

<p><code>setInterval()</code> is subject to the same throttling restrictions in Firefox as {{domxref("WindowOrWorkerGlobalScope.setTimeout","setTimeout()")}}; see <a href="/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setTimeout#Reasons_for_delays_longer_than_specified">Reasons for delays longer than specified</a>.</p>

<h2 id="规范">规范</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th>Specification</th>
   <th>Status</th>
   <th>Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('HTML WHATWG', 'webappapis.html#dom-setinterval', 'WindowOrWorkerGlobalScope.setInterval()')}}</td>
   <td>{{Spec2("HTML WHATWG")}}</td>
   <td>Method moved to the <code>WindowOrWorkerGlobalScope</code> mixin in the latest spec.</td>
  </tr>
  <tr>
   <td>{{SpecName("HTML WHATWG", "webappapis.html#dom-setinterval", "WindowTimers.setInterval()")}}</td>
   <td>{{Spec2("HTML WHATWG")}}</td>
   <td>Initial definition (DOM Level 0)</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容性">浏览器兼容性</h2>

<div>


<p>{{Compat("api.WindowOrWorkerGlobalScope.setInterval")}}</p>
</div>

<h2 id="参见">参见</h2>

<ul>
 <li><a href="/en-US/Add-ons/Code_snippets/Timers">JavaScript 定时器</a></li>
 <li>{{domxref("WindowOrWorkerGlobalScope.setTimeout")}}</li>
 <li>{{domxref("WindowOrWorkerGlobalScope.clearTimeout")}}</li>
 <li>{{domxref("WindowOrWorkerGlobalScope.clearInterval")}}</li>
 <li>{{domxref("window.requestAnimationFrame")}}</li>
 <li><a href="/en-US/Add-ons/Code_snippets/Timers/Daemons"><em>Daemons</em> management</a></li>
</ul>