How to Combine Two Arrays in JavaScript

Combining two arrays is a common task in JavaScript, and there are several methods to achieve this. Here’s a detailed guide on how to do it using different approaches.

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1. Using the concat() Method

The concat() method is a straightforward way to merge two or more arrays. It creates a new array by combining the elements of the arrays passed as arguments.

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

const combinedArray = array1.concat(array2);

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

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2. Using the Spread Operator

The spread operator (...) allows you to expand the elements of an array into another array. This method is concise and often preferred for its readability.

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

const combinedArray = [...array1, ...array2];

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

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3. Using push() with Spread Operator

You can also combine arrays by using the push() method in conjunction with the spread operator. This method modifies the original array by adding the elements of another array to it.

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

array1.push(...array2);

console.log(array1); // Output: [1, 2, 3, 4, 5, 6]

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4. Using Array.prototype.push() with apply()

Similar to the spread operator method, you can use the apply() method to combine arrays by pushing the elements of one array into another.

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

Array.prototype.push.apply(array1, array2);

console.log(array1); // Output: [1, 2, 3, 4, 5, 6]

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5. Using forEach() Method

You can also use the forEach() method to manually push elements of one array into another.

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

array2.forEach(element => array1.push(element));

console.log(array1); // Output: [1, 2, 3, 4, 5, 6]

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Conclusion

There are multiple ways to combine two arrays in JavaScript, each suited to different scenarios. The concat() method and the spread operator are commonly used for their simplicity and readability. Choose the method that best fits your needs based on whether you want to create a new array or modify an existing one.