Is there a JavaScript / jQuery DOM change listener?

Performance and compatibility considerations

The modern marvel that is MutationObserver outdoes the retired DOM3 mutation events like DOMNodeInserted or DOMAttrModified. With efficient design, it dodges the performance bullet plaguing the old guard.

For those nostalgic with DOMSubtreeModified, it had its charm — it offered a crack at detecting DOM changes in earlier years. But with great power comes great responsibility — beware of performance hit!

Don't let your MutationObserver get overwhelmed by the magnitude of DOM. Feed it specific selectors. Also, let it rest with disconnect() when it's no longer needed. It's not just courtesy, it's performance etiquette!

Extending jQuery's toolbox

Detect changes introduced by jQuery's html() method. How? Extend jQuery's prototype like so:

(function($) {
  const oldHtml = $.fn.html;
  $.fn.html = function() {
    const result = oldHtml.apply(this, arguments);
    if(arguments.length) $(this).trigger('contentchanged'); // Some HTML changed somewhere, let's make noise!
    return result;
  };
}(jQuery));

// Usage
$('#watchedElement').on('contentchanged', () => {
  console.log('The content changed! Someone touched the sacred HTML!'); // HTML change alert!
});
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Method extension - cool name, huh? - cleverly inserts custom events into jQuery, reinforcing its change detection prowess.

Dealing with live changes

If you're the patient type and need to check periodically for DOM changes—asynchronous plugin induced changes maybe? — dust off your setInterval powers:

setInterval(() => {
  // Pop a peek at element changes...
}, 1000);
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Adulterate this approach with MutationObserver to tackle spot-on and delayed change detection chores. Clockwork!

For navigation-centric DOM changes, add hashchange or popstate events to your bag of tricks. Single Page Applications (SPAs) love these bad boys for changing visible content without reloading:

window.addEventListener('hashchange', () => {
  // What's new in hashland?
});

window.addEventListener('popstate', () => {
  // Browser navigation bookkeeping
});


Library love: mutation-summary

MutationObserver is a beast. But what if we could filter mutations further? mutation-summary, enter stage!

const observer = new MutationSummary({
  callback: (summaries) => {
    const freshElements = summaries[0].added;
    // Your callback magic
  },
  queries: [{ element: 'div' }]
});


Hello to custom queries that reduce a flood of mutations to a gentle stream. Plus, get a neat summary of added and removed elements. Rockets your single-page applications to new heights!

Threading the compatibility needle

MutationObserver earns brownie points with its support across modern browsers. It's the standard-bearer for observing DOM changes. Keep an eye out for older browsers unaware of MutationObserver — polyfills or fallback strategies show them the ropes.

As a forward-thinker, pore over the specification documentation to make your codes future-proof. A stitch in time!

Power versus simplicity: The balance

MutationObserver is powerful. But sometimes you need a slingshot, not a cannon! jQuery's simplicity springs into action then. Need to detect a class change on one pesky element? Bind to a specific attribute change event via .on(). Easy and effective:

$('#targetElement').on('classChange', () => {
  // Classy changes call for classy responses
});
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Swing between the complexity of MutationObserver and the straightforwardness of jQuery. The right tool for the job, always!