How can I find the closest previous sibling with class using jQuery?

Performance and CPU intensity

Your code's efficiency often relates to how much of the DOM it has to traverse. While .prevAll('.yourClass').first() is convenient, it could be processor-intensive if you have long chains of sibling elements. It's because prevAll() searches through all preceding siblings.

Looking to increase performance with long chains? Here's the trick: combine the prevUntil() method with .last(). This combination stops once it finds the required selector. last() then retrieves the closest sibling of .yourClass:

// As they say on Reddit, "Did you just assume my .yourClass?"
var closestSibling = $('#element').prevUntil(':not(.yourClass)').last();
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This method is more computational-friendly as it won't make your CPU twiddle its electrons unnecessarily.

Handling dynamic classes

Your code needs to be as dynamic as your lifestyle. If you're dealing with a class name that changes based on a certain context, you can build your selector string to match:

// Your wish is my command!
var className = 'dynamicClass';
var closestSibling = $('#element').prevAll('.' + className).first();
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Coder, adapt thy method. This code will cover various situations where the class name isn't static.

Real-time Case Handling

Like a bad joke on Reddit, you never expect an error, when it pops, it's too late! Validation is key. Ensure your element selection is accurate:

// If closeSibling existed, well and good. Exit stage left!
if (closestSibling.length) {
    // Element exists, safe to proceed
} else {
    // Oops! Looks like you're in a class of your own.
}
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You've just made your code more error-tolerant. Congratulations! Here's a cookie 🍪!

Busting the Myths: prevAll vs. prev

Depending on your application, you might only need to check the direct previous sibling. Use the prev() method for this:

// Fire in the hole! Looking for direct sibling....Gotcha!
var closestSiblingDirect = $('#element').prev('.yourClass');
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Note that it only checks the immediate sibling. So, be sure that your target isn't playing hide and seek with other siblings.