How Can I Use jQuery to Detect Input Focus and Prevent Border Removal on Mouse Out?

Using jQuery to Determine Input Focus and Prevent Border Removal

In the quest to achieve cross-browser compatibility, the use of jQuery's .hover() method to mimic CSS's :hover on non- elements in Internet Explorer 6 has led to an unforeseen issue. When an input within one of these

s gains focus, the border created by the .hover() method disappears upon mouse out.

To resolve this, we seek to ascertain whether any input has focus upon mouse out. Since jQuery lacks a :focus selector, alternative methods are required.

jQuery 1.6 and Above

jQuery 1.6 includes a :focus selector, eliminating the need for custom implementations. Simply use $("..").is(":focus") to check for focused inputs.

jQuery 1.5 and Below

For earlier jQuery versions, it is recommended to define a custom :focus selector. This can be achieved with:

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

This ensures that only form controls and hyperlinks are considered focused.

Alternatively, you can use:

if ($("...").is(":focus")) { ... }

or:

$("input:focus").doStuff();

All jQuery Versions

To determine which element has focus, regardless of jQuery version, use:

$(document.activeElement)

Checking for Missing :focus Selector

If you are unsure of the jQuery version, you can add the :focus selector manually:

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

By employing these techniques, you can maintain the desired border behavior while adapting to browser-specific limitations.

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