#JS with() new Array method

The with method is a new addition to JavaScript's array methods introduced in ECMAScript 2023 (ES14). It allows you to create a new array with a value replaced at a specific index, without modifying the original array.

to solve this problem of mutability and achieve immutability while changing an element of an array.

The with() method takes two parameters:

• index - An index value which can start from 0, and also can be a negative number. The negative index counts backwards from the end of the array.
• value - The value to change at a given index.

Here's the syntax and an example of how to use the with method:

let originalArray = [1, 2, 3, 4, 5];
let newArray = originalArray.with(2, 99); // replaces the value at index 2 with 99

console.log(originalArray); // [1, 2, 3, 4, 5]
console.log(newArray); // [1, 2, 99, 4, 5]        

In this example:

• originalArray is the original array.
• originalArray.with(2, 99) creates a new array where the element at index 2 (which is 3) is replaced with 99.
• The original array remains unchanged, demonstrating the immutability of the operation.

As the with() method returns an array, you can chain the output of the with() method along with other array methods, like map(), filter(), reduce(), some(), every() etc.