Using jQuery to test if an input has focus

Advanced topics in focus identification

Establishing focus selectors for older jQuery versions

Users on jQuery versions below 1.6 don't have the :focus selector. For these dark ages, we can create our own special focus selector:

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

With this snippet, you can add focus usability even with older jQuery versions. No discrimination against the oldies!

Real-time focus change detection

Let's dynamically react to focus changes. We should use jQuery's .on() for this:

$('input').on('focus', function() {
  $(this).addClass('focused'); // Make input feel loved on focus
}).on('blur', function() {
  $(this).removeClass('focused'); // Break up when input loses focus
});


This events handling helps your users feel the love their input is (or isn't) getting by adding or removing a CSS class on focus changes.

Detecting focus in dynamically added content

Just because an input was late to the party doesn't mean it should get ignored. Use event delegation to handle focus for dynamically added inputs:

$(document).on('focusin', 'input', function() {
  // Your move when an input is focused
});


With focusin, no input, no matter how fashionably late, will be overlooked.

Tackling cross-browser compatibility

Playing nice with older browsers

The cool kids (read: modern browsers) handle focus in similar ways. But older browsers, like IE6, often like to play by their own rules. Always check compatibility across multiple browsers to ensure all users get the same experience.

Using focus to imitate hover in retro browsers

Older browsers like IE6 sometimes need a little extra help. If you're working with such oddballs, you can get :focus to play :hover:

$('input').on('focus', function() {
  $(this).addClass('hover'); // Playing dress-up as hover on focus
}).on('blur', function() {
  $(this).removeClass('hover'); // Back to reality on blur
});


Enhancing visibility with focus

Help your users out by visually highlighting focused elements. This not only improves UX but also boosts accessibility:

$('input').on('focus', function() {
  $(this).css('border-color', 'blue'); // The color of attention! Yay!
}).on('blur', function() {
  $(this).css('border-color', ''); // Back to being the boring, attention-lacking input
});


Writing comprehensive jQuery code for focus handling

As we strive for code elegance, it's important to remember:

• Manage focus on all form elements: inputs, textareas, selects, even links.
• Mind false positives—not all elements can have focus.
• Validate focus state before making changes to avoid hasty, regrettable decisions.
• Cherry pick proven solutions from GitHub or developer blogs by reputable developers.

Ensuring readability for future code maintenance

Just like overdoing makeup, code that's too complex will scare people off. Strive for simplicity for easier maintenance.