Detecting Duplicates In An Array In JavaScript

I came across this problem and thought I would share my solution.

I did a bit of Google-Fu and found a pretty good answer here:

Stack Overflow post.

However, I just wanted to know if any duplicates EXISTED. I didn’t care about what they were, so I adapted the solution below:

    var checkForDuplicateValues = function(theArray) {
        var placeHolder = theArray.length,

        while(comparePlaceHolder=--placeHolder) {
            while(comparePlaceHolder--) {
                if(!(theArray[placeHolder]!== theArray[comparePlaceHolder])) {
                    return true;

        return false;

I hope this helps! As always leave a comment to provide constructive feedback!

Don Marges

Don Marges

Fullstack Web Developer

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