These change the original array (important in interviews)

Adds/removes elements at a specific index.

const arr = [10, 20, 30, 40];
arr.splice(1, 2);
// removes 2 items starting at index 1
// arr = [10, 40]

e:** O(n) Mutates original? Yes### Insert using splice

const arr = [10, 30];
arr.splice(1, 0, 20);
// [10, 20, 30]

Adds to end.

arr.push(50);

Time: O(1) amortized Mutates? Yes

Removes from end.

arr.pop();

Time: O(1) Mutates? Yes

Adds to start.

arr.unshift(5);

Time: O(n) Mutates? Yes

Removes from start.

arr.shift();

Time: O(n) Mutates? Yes

Reverses the array in place.

arr.reverse();

Time: O(n) Mutates? Yes

Sorts the array in place.

arr.sort((a, b) => a - b);

Time: O(n log n) Mutates? Yes

Always pass comparator for numbers.