JS Timing

更新時(shí)間：2007年04月21日 00:00:00 作者：

使用JS是可以讓函數(shù)不直接執(zhí)行的，而是在過(guò)了一個(gè)指定的時(shí)間間隔后才執(zhí)行。這就叫做事件事件。
With JavaScript, it is possible to execute some code NOT immediately after a function is called, but after a specified time interval. This is called timing events.
使用JS是可以讓函數(shù)不直接執(zhí)行的，而是在過(guò)了一個(gè)指定的時(shí)間間隔后才執(zhí)行。這就叫做事件事件。
JavaScript Timing Events
JS時(shí)間事件
With JavaScript, it is possible to execute some code NOT immediately after a function is called, but after a specified time interval. This is called timing events.
使用JS是可以讓函數(shù)不直接執(zhí)行的，而是在過(guò)了一個(gè)指定的時(shí)間間隔后才執(zhí)行。這就叫做事件事件。
It's very easy to time events in JavaScript. The two key methods that are used are:
JS的時(shí)間事件是非常簡(jiǎn)單的。使用了兩個(gè)關(guān)鍵的方法：
    * setTimeout() - executes a code some time in the future
      在一些時(shí)間后執(zhí)行代碼
    * clearTimeout() - cancels the setTimeout()
      取消setTimeout()
Note: The setTimeout() and clearTimeout() are both methods of the HTML DOM Window object.
注意：setTimeout() 和 Timeout() 都是HTML DOM Window 對(duì)象的方法。
setTimeout()
Syntax語(yǔ)法
var t=setTimeout("javascript statement",milliseconds)
The setTimeout() method returns a value - In the statement above, the value is stored in a variable called t. If you want to cancel this setTimeout(), you can refer to it using the variable name.
setTimeout()方法返回一個(gè)值 - 在上面的聲明里，值被保存在變量t中。如果你想取消這個(gè)setTimeout()可以使用變量名來(lái)提出它（用clearTimeout(t)）
The first parameter of setTimeout() is a string that contains a JavaScript statement. This statement could be a statement like "alert('5 seconds!')" or a call to a function, like "alertMsg()".
setTomeout()的第一個(gè)參數(shù)是字符串聲明。它可以像"alert('5 seconds!')"或是調(diào)用一個(gè)函數(shù)像"alertMsg()"
The second parameter indicates how many milliseconds from now you want to execute the first parameter.
第二個(gè)參數(shù)用來(lái)表明從現(xiàn)在開(kāi)始你希望在多少毫秒后執(zhí)行第一個(gè)參數(shù)
Note: There are 1000 milliseconds in one second.
1000毫秒為一秒
Example
舉例
When the button is clicked in the example below, an alert box will be displayed after 5 seconds.
當(dāng)下面的按鈕被點(diǎn)擊后，每過(guò)5秒就會(huì)出現(xiàn)一個(gè)警告框。
<html>
<head>
<script type="text/javascript">
function timedMsg()
{
var t=setTimeout("alert('5 seconds!')",5000)
}
</script>
</head>
<body>
<form>
<input type="button" value="Display timed alertbox!"
onClick="timedMsg()">
</form>
</body>
</html>
Example - Infinite Loop
無(wú)限循環(huán)
To get a timer to work in an infinite loop, we must write a function that calls itself. In the example below, when the button is clicked, the input field will start to count (for ever), starting at 0:
要得到一個(gè)無(wú)限循環(huán)的記時(shí)器，我們必須寫(xiě)出一個(gè)自我調(diào)用的函數(shù)。下面的例子，當(dāng)按鈕按下后，輸入框就會(huì)從0開(kāi)始記數(shù)（永遠(yuǎn)的）
<html>
<head>
<script type="text/javascript">
var c=0
var t
function timedCount()
{
document.getElementById('txt').value=c
c=c+1
t=setTimeout("timedCount()",1000)
}
</script>
</head>
<body>
<form>
<input type="button" value="Start count!"
onClick="timedCount()">
<input type="text" id="txt">
</form>
</body>
</html>
clearTimeout()
Syntax語(yǔ)法
clearTimeout(setTimeout_variable)
Example
舉例
The example below is the same as the "Infinite Loop" example above. The only difference is that we have now added a "Stop Count!" button that stops the timer:
下面的例子和上面的“無(wú)限循環(huán)”差不多。唯一的不同就是我們現(xiàn)在多了一個(gè)“停止記數(shù)”的按鈕來(lái)停止記時(shí)器。
<html>
<head>
<script type="text/javascript">
var c=0
var t
function timedCount()
{
document.getElementById('txt').value=c
c=c+1
t=setTimeout("timedCount()",1000)
}
function stopCount()
{
clearTimeout(t)
}
</script>
</head>
<body>
<form>
<input type="button" value="Start count!"
onClick="timedCount()">
<input type="text" id="txt">
<input type="button" value="Stop count!"
onClick="stopCount()">
</form>
</body>
</html>