JavaScript: Merge two arrays and removes all duplicates elements

JavaScript Array: Exercise-30 with Solution

Merge Arrays Without Duplicates

Write a JavaScript function that merges two arrays and removes all duplicate elements.

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

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to merge two arrays, removing duplicates and maintaining the order
function merge_array(array1, array2) {
 // Initialize an empty array to store the result
 var result_array = [];
 
 // Concatenate both arrays to form a new array
 var arr = array1.concat(array2);
 
 // Get the length of the new array
 var len = arr.length;
 
 // Initialize an empty object to keep track of unique items
 var assoc = {};
 // Iterate through the array in reverse order
 while (len--) {
 // Get the current item from the array
 var item = arr[len];
 // Check if the item is not already in the result array
 if (!assoc[item]) { 
 // Add the item to the beginning of the result array
 result_array.unshift(item);
 
 // Mark the item as seen in the associative object
 assoc[item] = true;
 }
 }
 // Return the result array with unique items
 return result_array;
}
// Example arrays for testing
var array1 = [1, 2, 3];
var array2 = [2, 30, 1];
// Output the result of merging the arrays
console.log(merge_array(array1, array2));

Output:

[3,2,30,1]

Flowchart:

ES6 Version:

// Function to merge two arrays, removing duplicates and maintaining the order
const mergeArray = (array1, array2) => {
 // Initialize an empty array to store the result
 const resultArray = [];
 
 // Concatenate both arrays to form a new array
 const arr = array1.concat(array2);
 
 // Get the length of the new array
 let len = arr.length;
 
 // Initialize an empty object to keep track of unique items
 const assoc = {};
 // Iterate through the array in reverse order
 while (len--) {
 // Get the current item from the array
 const item = arr[len];
 // Check if the item is not already in the result array
 if (!assoc[item]) { 
 // Add the item to the beginning of the result array
 resultArray.unshift(item);
 
 // Mark the item as seen in the associative object
 assoc[item] = true;
 }
 }
 // Return the result array with unique items
 return resultArray;
};
// Example arrays for testing
const array1 = [1, 2, 3];
const array2 = [2, 30, 1];
// Output the result of merging the arrays
console.log(mergeArray(array1, array2));

Live Demo:

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

For more Practice: Solve these Related Problems:

• Write a JavaScript function that merges two arrays and removes duplicates using the Set data structure.
• Write a JavaScript function that combines two arrays and filters out duplicates using the filter() method.
• Write a JavaScript function that manually iterates through both arrays and adds only unique elements to a new array.
• Write a JavaScript function that handles merging arrays with mixed data types and returns a duplicate-free array.

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• JavaScript array Exercises Home ↩
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