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.

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