In this article, we will look at how to merge two arrays and remove duplicates in JavaScript. 

Why Merge Two Arrays?

There are many reasons why we need to merge two arrays. For example, in a database, we might need to merge two arrays of records based on a common field. In a web application, we must combine the results of two different API calls into a single array. Regardless of the reason, merging two arrays is a common operation in JavaScript, and understanding how to do it is essential for any web developer.

Removing Duplicates

There are many reasons why we need to merge two arrays. For example, in a database, we might need to merge two arrays of records based on a common field. In a web application, we must combine the results of two API calls into a single array. Regardless of the reason, merging two arrays is a common operation in JavaScript, and understanding how to do it is crucial for any web developer.

Merging Two Arrays and Removing Duplicates

The easiest way to merge two arrays and remove duplicates in Javascript is to use the concat method and the Set object. The concat method allows us to combine two arrays into a single array. Using the Set object to remove duplicates, we can ensure that unique values are stored in the merged array.

Method 1: Using the Spread Operator and the Set Object

One way to merge two arrays and remove duplicates is to use the spread operator (…) and the Set object. The spread operator allows you to spread the elements of an array into individual elements, while the Set object stores unique values.

Here is an example of how to use these features to merge two arrays and remove duplicates:

				
					const array1 = [1, 2, 3, 4];
const array2 = [3, 4, 5, 6];

const mergedArray = [...new Set([...array1, ...array2])];

console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]

In the example above, we first spread the elements of array1 and array2 into individual components using the spread operator. We then pass this array to the Set constructor, removing duplicate elements and storing the unique values. Finally, we spread the Set object into an array using the spread operator, which gives us the desired result: a merged array with no duplicate elements.

				
					function removeDuplicates(arr) {
  return arr.filter((item, index) => arr.indexOf(item) === index);
}

const numbers = [1, 2, 3, 3, 4, 4, 5];
console.log(removeDuplicates(numbers)); // [1, 2, 3, 4, 5]

Method 2: Using the Array.prototype.reduce

Another way to merge two arrays and remove duplicates is to use the Array.prototype.reduce method. The reduce method allows you to reduce an array to a single value by applying a function to each array element.

Here is an example of how to use the reduce method to merge two arrays and remove duplicates:

				
					const array1 = [1, 2, 3, 4];
const array2 = [3, 4, 5, 6];

const mergedArray = array1.concat(array2).reduce((accumulator, currentValue) => {
  if (!accumulator.includes(currentValue)) {
    accumulator.push(currentValue);
  }
  return accumulator;
}, []);

console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]

In the example above, we first use the Array.prototype.concat method to merge the two arrays into a single array. We then use the reduce method to iterate over this array and push each unique element into a new array, which we pass as the accumulator. The resulting array is the merged array with no duplicate elements.

No matter which approach you choose, it is crucial to keep in mind that removing duplicates from an array can be an important part of many programs. Using one of the methods described above, you can easily remove duplicates from an array in JavaScript.


Thanks for reading. Happy coding!