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How to Insert into Array at an Index Without Mutation in JavaScript 📌[All Method]️

It’s also a question How to Insert into Array at an Index Without Mutation in JavaScript? What should you do if you come across a code error! Let’s get started on fixing it.
Question: What is the best solution for this problem? Answer: This blog code can help you solve errors How to Insert into Array at an Index Without Mutation in JavaScript. Question: What are the reasons for this code mistake and how can it be fixed? Answer: You can find a solution by following the advice in this blog.

Most array insert methods require modifying the original array, but how can we avoid mutation and return a new array with the inserted element?

Insert With Mutation

We know we can use splice() to insert items into an array at some specified index.

let arr = ["one", "two", "four"];
arr.splice(2, 0, "three");
console.log(arr); // ["one", "two", "three", "four"]

Insert Without Mutation

We can create an insert() function that will use the ES6 spread operator to insert the array items around the inserted item.

const insert = (arr, index, ...newItems) => [
  ...arr.slice(0, index),
  ...newItems,
  ...arr.slice(index)
];

arr.slice(0, index) is grabbing the array elements before the specified index.

arr.slice(index) is grabbing the array elements after the specified index.

Suppose we have ...arr. The ..., or spread operator, will “drop” the array arr and instead return its values.

const arr1 = ["one", "two", "four"];
const arr2 = insert(arr1, 2, "three");
console.log(arr2); // ["one", "two", "three", "four"]

We can also insert multiple elements at once.

const arr1 = ["one", "two", "five"];
const arr2 = insert(arr1, 2, "three", "four");
console.log(arr2); // ["one", "two", "three", "four", "five"]


Now you learned, How you can use & How to Insert into Array at an Index Without Mutation in JavaScript.
Final Note: Try to Avoid this type of mistake(error) in future!

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