How to remove duplicates from JavaScript Array?


Posted On: Feb 22, 2018


There are many ways to remove duplicates from JavaScript array. These are described below with examples:

1. By using Set: It is the simplest approach to remove duplicates. Set is an inbuilt object to store unique values in an array. Here's how we use set:

    function uniquearray(array) { 
       let unique_array= Array.from(set(array)) 
       return unique_array;}

As in the above code, you created a set of an array which automatically eliminates the duplicate values.

2. By using Filter: Another approach to remove duplicates from an array is applying filter on an array. To call filter method, it requires three arguments: array, current element, index of current element. Here’s how we use filter:

function unque_array (arr){
 let unique_array = arr.filter(function(elem, index, self) {
 return index == self.indexOf(elem); } 
return unique_array }

3. By using for loop: In this, we can use for loop to remove duplicates. In this we make an empty array in which those elements will be added from the duplicate array which are not present in this before. Thus, finally we will get an array which has unique elements. Code to implement this:

Array dups_names = ['Ron', 'Pal', 'Fred', 'Rongo', 'Ron'];
function dups_array(dups_names) {
 let unique = {};
 names.forEach(function(i) {
    If (!unique[i]) {
      unique[i] = true;    }
return Object.keys(unique);}   // Ron, Pal, Fred, Rongo

These are the main three methods used in JavaScript to get a unique array.

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