如何使用 jQuery 檢查輸入是否有焦點？-js教程-PHP中文網

如何使用 jQuery 檢查輸入是否有焦點？

Patricia Arquette

發布： 2024-11-15 03:22:02

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How to Check if an Input Has Focus Using jQuery?

Using jQuery to Test if an Input Has Focus

This dilemma arises when using jQuery to replicate CSS :hover behavior for elements other than in IE6. The border surrounding the

disappears when an input within the form gains focus and the mouse cursor hovers in and out.

To address this, jQuery can be used to check if any input within the form has focus. However, as jQuery lacks a :focus selector, alternative methods must be employed.

jQuery 1.6+

With jQuery 1.6 and above, a :focus selector is available. The following code can be used to check for focus:

$("..").is(":focus")

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jQuery 1.5 and Below

For earlier jQuery versions, the following code can be used to define a new selector and check for focus:

jQuery.expr[':'].focus = function(elem) {
  return elem === document.activeElement &amp;&amp; (elem.type || elem.href);
};

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Alternatively, you can check which element has focus using:

$(document.activeElement)

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For All jQuery Versions

To ensure compatibility with different jQuery versions, you can add the :focus selector as follows:

(function ($) {
  var filters = $.expr[":"];
  if (!filters.focus) {
    filters.focus = function(elem) {
      return elem === document.activeElement &amp;&amp; (elem.type || elem.href);
    };
  }
})(jQuery);

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By testing for focus, the border can be prevented from disappearing when an input gains focus and the cursor hovers in and out.

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