document.getElementById（）。focus（）返回undefined
[英]document.getElementById().focus() returning undefined
问题描述
I have the following HTML: 
我有以下HTML：
<input type="text" id="endDateEditBox" value="" style="margin-left:5px; height:18px; width:70px; vertical-align:middle;" onchange="validateDate('endDateEditBox', $(dateFormatErrorString).value)">
And I am trying to make this focus using the following Javascript: 我正在尝试使用以下Javascript进行此焦点：
document.getElementById("endDateEditBox").focus();
Which chrome console and Firebug both return as undefined. 哪个chrome控制台和Firebug都返回undefined。 I feel like I am missing something very obvious here, can anyone help? 我觉得我错过了一些非常明显的东西，有人可以帮忙吗？
3 个解决方案
解决方案1
23 已采纳 2012-02-03 11:23:32
The focus() method does not return a value. focus()方法不返回值。 It sets the focus on the matched input, and then returns undefined ... 它将焦点设置在匹配的输入上，然后返回undefined ...
解决方案2
1 2012-02-03 11:28:22
The Javascript native focus function doesn't return anything. Javascript本机焦点功能不返回任何内容。
If you expected to receive the element and use it in concatenation, you're probably confusing it with the jQuery's focus function . 如果您希望接收元素并在连接中使用它，那么您可能会将它与jQuery的焦点函数混淆。
解决方案3
0 2012-02-03 11:42:53
Try this code: 试试这段代码：
<html>
<head>
<script type="text/javascript">
function setFocus()
{
document.getElementById("endDateEditBox").focus();
}
</script>
</head>
<body onload="setFocus()">
<form>
Date: <input type="text" id="endDateEditBox"><br />
</form>
</body>
</html>
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