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How To Find Duplicate Values In Array Using JavaScript

Last Updated : Jul 1, 2023

How To Find Duplicate Values In Array Using JavaScript

In this tutorial we will show you the solution of how to find duplicate values in array using JavaScript, here we using two nested for loops for iterate each array elements with remaining array elements then only we can found duplicates easily using if condition we can easily compare each other values.

When if condition will true means we had both original and duplicated in our hands then we can do any other process if needed.

Step By Step Guide On How To Find Duplicate Values In Array Using JavaScript :-

Here we defined nested for loop we can compare each other values.

In first for loop iterate will start from index ‘0th’ position then we have to compare that value with remaining value in array so we defined second for loop from next index of current value in first for loop till condition meets last value in array then we printed on console so we have to open console for seeing result of duplicated value.

<!DOCTYPE html>
<html>
    <head>
        <title>FIND DUPLICATES IN ARRAY</title>
    </head>
    <body>
    <script>
            const arr=['12','34','45','89','45','12'];
            for(i=0;i<arr.length;i++){
                for(j=i+1;j<arr.length;j++){
                    if(arr[i] == arr[j]){
                        console.log(arr[i]);
                        break;
                    }
                }
            }
        </script>
    </body>
</html>
  1. <!DOCTYPE html> tag which is instruct the web browser about what version of HTML file written in and it’s not have any ending tag.
  2. The<html> tag is used to indicate the beginning of HTML document.
  3. As above shown <head> tag is contain information about webpage and external file links are declared here. <title> tag is used for set the webpage title.
  4. Both <head> and <title> tags having their pair end tag, so we need to close the ending tags respectively. If you’re not closed anyone of ending tag properly that is also affect the webpage result.
  5. <body> tag is beginning of main coding part because it contain coding of entire website blocks and elements described here.
  6. Here we defined in script we declared array variable ‘arr’ for initialize values ‘['12','34','45','89','45','12']’.
  7. In first for loop we iterating array elements from index ‘0’ then in second for loop we iterating remaining array elements from next index of first loop value each times.
  8. Then within that using if condition we checking each other values of remaining index of values. When if condition will true then we immediately printed on console by console.log() method.
  9. The break statement will stops the second for loop iterations after found duplicate so it will start from first for loop for iterate next value.
  10. Both </body>,</html> tags closed respectively. </body> tag indicates the end of body, Then </html> tag indicates the end of HTML document.

Conclusion :-

In conclusion now we are able to know how to find duplicates from array using javascript.

When we executes program on browser we can’t see the result because we displayed on console so we need to use shortcut ‘ctrl+shift+j’ on browser then console panel will open at right hand side with result of duplicated values in array.

We can also change array ‘arr’ with some other values or we can define array with string values.

I hope this tutorial on how to find duplicate values in array using JavaScript helps you and the steps and method mentioned above are easy to follow and implement.