为什么blur（）无法工作？
[英]why the blur() can't work?
问题描述
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>test</title>
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">
$('#target').blur(function() {
alert('welcome,boy.');
})
</script>
</head>
<body>
<form>
<input id="target" type="text" value="Field 1" />
<input type="text" value="Field 2" />
</form>
<div id="other">
Trigger the handler
</div>
</body>
</html>
the jquery.js is in my js file, i put the above code in a file named test.html. 
jquery.js在我的js文件中，我将上面的代码放在一个名为test.html的文件中。 when i click the first input textbox then click at other place. 当我单击第一个输入文本框，然后在其他地方单击时。 there is no popup an alert box? 没有弹出警报框？
2 个解决方案
解决方案1
3 已采纳 2011-03-28 02:44:57
The script runs immediately when the browser reads it in the HTML, which is before it even looks at the body. 当浏览器从HTML中读取脚本时，该脚本将立即运行，甚至在查看正文之前。 When the script runs, the #target element doesn't exist yet. 脚本运行时， #target元素尚不存在。
One solution would be to move the script to the bottom of <body> . 一种解决方案是将脚本移到<body>的底部。 Another would be to use jQuery's DOM ready function: 另一个方法是使用jQuery的DOM ready函数：
$(function() {
$('#target').blur(function() {
alert('welcome,boy.');
});
});
In that case, you could still put the script at the head, and the script itself would run. 在这种情况下，您仍然可以将脚本放在最前面，脚本本身将运行。 However, it would put off running the part inside the $(function () { /* code here */ } ) wrapper until the browser has read all of the HTML and has built its nice tree of DOM elements. 但是，它将推迟在$(function () { /* code here */ } )运行该部分，直到浏览器读取所有HTML并构建其漂亮的DOM元素树为止。
解决方案2
3 2011-03-28 02:45:30
It's because #target doesn't exist when that code executes. 这是因为执行该代码时#target不存在。 Try this: 尝试这个：
<script type="text/javascript">
$(function(){
$('#target').blur(function() {
alert('welcome,boy.');
});
});
</script>
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