Javascript 使用 jQuery 检查文本框焦点
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Check textbox focus using jQuery
提问by user853575
Possible Duplicate:
Using jQuery to test if an input has focus
可能的重复：
使用 jQuery 测试输入是否具有焦点
I need to check if a particular textbox has the focus or not using jQuery. So my code is like this, but it is not working:
我需要使用 jQuery 检查特定文本框是否具有焦点。所以我的代码是这样的，但它不起作用：
if (document.getElementById("lastname").focus = true) {
alert("hello");
}
My use-case is this: I have a textbox which should be shown or hidden when the #lastnametextbox gains or loses focus. However, if the #lastnametextbox loses the focus to the other textbox, the latter should remain visible until it loses focus as well.
我的用例是这样的：我有一个文本框，当#lastname文本框获得或失去焦点时，它应该显示或隐藏。但是，如果#lastname文本框失去对另一个文本框的焦点，则后者应该保持可见，直到它也失去焦点。
Any help will be appreciated.
任何帮助将不胜感激。
回答by nbrooks
if ($("#lastname").is(':focus')) {
alert("hello");
}
jQuery docs for :focus
jQuery docs for .is()
Update:更新：要在字段获得/失去焦点时显示/隐藏元素，请使用
focusinfocusin和focusoutfocusout事件处理程序：$(document).ready(function() {
$('#lastname').focusin(function() {
$(hidden-element).show();
}).add(hidden-element).focusout(function() {
if ( !$(hidden-element).is(':focus') ) {
$(hidden-element).hide();
}
});
});
//where hidden-element is a reference to or selector for your hidden text field
回答by redDevil
$("#lastname").focus(function(){
alert("lastname has focus");
});
回答by rowasc
if (document.getElementById("lastname").focus == true) {
alert("hello");
}
Check with == , using = is an assignment
检查 == ，使用 = 是一个赋值
回答by gerky
回答by Anant Dabhi
<script type="text/javascript" language="javascript">
function check() {
if ($(document.activeElement).attr("id") === "element_name") {
alert('checkbox is focused');
}
}
</script>
回答by VBH
Try this
尝试这个
var status = $('#lastname').is(":focus");
alert(status);//false or true
