In JavaScript, Merge Two Arrays and Remove Duplicates

4 min readFeb 18, 2024

In JavaScript, Merge Two Arrays and Remove Duplicates

Learn different methods to merge two arrays and remove duplicate elements in JavaScript. Code examples and explanations provided. Choose the most suitable method for your project.

3 methods In JavaScript, Merge Two Arrays and Remove Duplicates

Learn different methods to merge two arrays and remove duplicate elements in JavaScript. Code examples and explanations provided. Choose the most suitable method for your project.

Introduction

JavaScript is a versatile programming language that allows developers to manipulate and work with arrays efficiently. One common task is merging two arrays and removing any duplicate elements. In this blog post, we will explore different methods to achieve this in JavaScript, along with code examples.

Method 1: Using the Spread Operator and Set

The spread operator (…) allows us to expand an iterable object, such as an array, into individual elements. We can use this operator along with the Set object to merge two arrays and remove duplicates.

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

const mergedArray = [...new Set([...array1, ...array2])];console.log(mergedArray);
// Output: [1, 2, 3, 4]

In the above example, we first use the spread operator to combine the elements of array1 and array2 into a new array. We then create a Set object from this new array, which automatically removes any duplicate elements. Finally, we use the spread operator again to convert the Set back into an array.

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Method 2: Using the concat() Method and Set

The concat() method in JavaScript can be used to merge two or more arrays. By combining this method with the Set object, we can achieve the desired result.

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

const mergedArray = Array.from(new Set(array1.concat(array2)));console.log(mergedArray);
// Output: [1, 2, 3, 4]

In this example, we first use the concat() method to merge array1 and array2 into a new array. We then create a Set object from this new array using the Array.from() method, which converts the Set back into an array.

Method 3: Using the filter() Method

The filter() method in JavaScript allows us to create a new array with all elements that pass a certain condition. We can use this method to filter out duplicate elements while merging two arrays.

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

const mergedArray = array1.concat(array2).filter((value, index, self) => {
  return self.indexOf(value) === index;
});console.log(mergedArray);
// Output: [1, 2, 3, 4]

In this example, we first merge array1 and array2 using the concat() method. Then, we apply the filter() method to the merged array. The filter() callback function checks if the current element’s index is the same as its first occurrence in the array. If it is, the element is included in the new array; otherwise, it is filtered out.

Method 4: Using the reduce() Method

The reduce() method in JavaScript allows us to reduce an array to a single value by applying a function to each element. We can use this method to merge two arrays and remove duplicates.

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

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]

In this example, we first merge array1 and array2 using the concat() method. Then, we apply the reduce() method to the merged array. The reduce() callback function checks if the current element is already present in the accumulator array. If it is not, the element is added to the accumulator using the push() method. Finally, the accumulator is returned as the result.

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Conclusion

Merging two arrays and removing duplicates is a common task in JavaScript. We have explored several methods to achieve this, including using the spread operator and Set, concat() method and Set, filter() method, and reduce() method. Depending on the specific requirements and preferences, developers can choose the most suitable method for their projects. By understanding and utilizing these techniques, JavaScript developers can efficiently merge arrays and eliminate duplicate elements from their code.

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