What are the array mutation methods?

JavaScript array methods can be categorized into two groups:

1. Mutating methods: These are the methods that directly modify the original array.
2. Non-mutating methods: These methods return a new array without altering the original one.

There are 9 methods in total that mutate the arrays,

1. push: Adds one or more elements to the end of the array and returns the new length.
2. pop: Removes the last element from the array and returns that element.
3. unshift: Adds one or more elements to the beginning of the array and returns the new length..
4. shift: Removes the first element from the array and returns that element.
5. splice: Adds or removes elements from the array at a specific index position.
6. sort: Sorts the elements of the array in-place based on a given sorting criteria.
7. reverse: Reverses the order of elements in the given array.
8. fill: Fills all elements of the array with a specific value.
9. copyWithIn: Copies a sequence of elements within the array to a specified target index in the same array.

Practical Code Example

// Array Mutation Methods (modify array in place):
// push(), pop(), shift(), unshift(), splice(), sort(), reverse()

// Modern Non-Mutating Alternatives (ES2023):
const original = [3, 1, 2];
const sorted = original.toSorted();     // [1, 2, 3] (original stays [3, 1, 2])
const reversed = original.toReversed(); // [2, 1, 3]
const spliced = original.toSpliced(0, 1, 99); // [99, 1, 2]