JavaScript: Merge two arrays and removes all duplicates elements

Last update on May 30 2022 10:08:33 (UTC/GMT +8 hours)

JavaScript Array: Exercise-30 with Solution

Write a JavaScript function to merge two arrays and removes all duplicates elements.

Test data:
var array1 = [1, 2, 3];
var array2 = [2, 30, 1];
console.log(merge_array(array1, array2));
[3, 2, 30, 1]

Pictorial Presentation:

JavaScript: Merge two arrays and removes all duplicates elements

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript function to merge two arrays and removes all duplicates elements.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function merge_array(array1, array2) {
    var result_array = [];
    var arr = array1.concat(array2);
    var len = arr.length;
    var assoc = {};

    while(len--) {
        var item = arr[len];

        if(!assoc[item]) 
        { 
            result_array.unshift(item);
            assoc[item] = true;
        }
    }

    return result_array;
}


var array1 = [1, 2, 3];

var array2 = [2, 30, 1];

console.log(merge_array(array1, array2));

Sample Output:

[3,2,30,1]

Flowchart:

ES6 Version:

function merge_array(array1, array2) {
    const result_array = [];
    const arr = array1.concat(array2);
    let len = arr.length;
    const assoc = {};

    while(len--) {
        const item = arr[len];

        if(!assoc[item]) 
        { 
            result_array.unshift(item);
            assoc[item] = true;
        }
    }

    return result_array;
}


const array1 = [1, 2, 3];

const array2 = [2, 30, 1];

console.log(merge_array(array1, array2));

Live Demo:

See the Pen JavaScript - Merge two arrays and removes all duplicates elements - array-ex- 30 by w3resource (@w3resource) on CodePen.

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Next: Write a JavaScript function to remove a specific element from an array.

JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = []; arr[0] = "Jani"; arr[1] = "Hege"; arr[2] = "Stale"; arr[3] = "Kai Jim"; arr[4] = "Borge"; console.log(arr.join()); arr.splice(2, 0, "Lene"); console.log(arr.join());

Ref: https://bit.ly/2BXbp04