How to clone an array in JavaScript ?

In JavaScript, cloning an array means creating a new array with the same elements as the original array. Cloning an array in JavaScript is useful when you want to create a new array that has the same elements as an existing array, without modifying the original array.

When to clone array?

If you want to perform some operations on an array, such as sorting, filtering, or mapping, but you don’t want to modify the original array, you can create a clone of the original array and perform the operations on the clone instead.

• When passing an array to a function as an argument, you may want to ensure that the function does not modify the original array. In this case, you can pass a clone of the array instead.
• If you want to preserve the original array for future reference, you can create a clone of the original array and use the clone for further processing or manipulation.
• If you have an array that contains objects or arrays as elements, and you want to avoid modifying the original objects or arrays, you can create a clone of the array to work with, so that changes to the objects or arrays in the clone do not affect the original objects or arrays.

Thus, cloning an array in JavaScript is a useful technique for working with arrays in a way that preserves the integrity of the original array and its elements.

Here are some common use cases for cloning an array:

Using the Array.slice() Method

We use the slice method to create a shallow copy of an array. This method creates a new array with a subset of the elements from the original array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = originalArray.slice();
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the spread Operator

Using the spread operator … is a concise and easy way to clone an array in JavaScript. The spread operator allows you to expand an array into individual elements, which can then be used to create a new array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = [...originalArray];
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Array.from() Method

Using the Array.from() method is another way to clone an array in JavaScript. This method creates a new array from an existing array, using an optional mapping function to transform the values in the new array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = Array.from(originalArray);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Array.concat() Method

Using the Array.concat() method is another way to clone an array in JavaScript. This method creates a new array by concatenating two or more arrays together.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = [].concat(originalArray);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using a for loop

This method involves iterating through each element in the original array and copying each element into a new array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = [];
for (let i = 0; i < originalArray.length; i++) {
    clonedArray.push(originalArray[i]);
}
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Array.map() Method

Using the Array.map() method is another way to clone an array in JavaScript. This method creates a new array by mapping each element from the original array to a new value.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = originalArray.map(x => x);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Array.from() method with a map function

Using the Array.from() method with a map function is another way to clone an array in JavaScript. This method creates a new array by mapping each element from the original array to a new value using a provided function.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = Array.from(originalArray, x => x);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Array.of() Method

This method creates a new array with the same elements as the original array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = Array.of(...originalArray);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the JSON.parse() and JSON.stringify() Methods

Using the JSON.parse() and JSON.stringify() methods is another way to clone an array in JavaScript. This method involves converting the original array to a JSON string and then parsing the JSON string to create a new array.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = JSON.parse(JSON.stringify(originalArray));
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Using the Object.assign() Method

Using the Object.assign() method is another way to clone an array in JavaScript. This method creates a new array by copying the properties of the original array to a new object.

Example: This example shows the implementation of the above-explained approach.

Javascript

const originalArray = [1, 2, 3];
const clonedArray = Object.assign([], originalArray);
console.log(clonedArray);

Output

[ 1, 2, 3 ]

Note: Thus, When cloning an array, it is important to consider the complexity of the data and the performance requirements of the application.