How to Use the splice() Method

The basic idea of the splice()method is as follows:
splice(start, deleteCount, item1, item2, itemN)

Parameter 1: start is the index at which to start changing the array.
Parameter 2: deleteCount is an integer indicating the number of elements in the array to remove from start.
Parameter 3: Items are the elements to add to the array, beginning from start.

!! IMPORTANT !!
The splice() method modifies the original array and returns an array of the deleted items.

Case 1: Only Setting start

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(2);
console.log(numbers);  // [0, 1]
console.log(removedNumbers);  // [2, 3, 4]

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(-3);
console.log(numbers);  // [0, 1]
console.log(removedNumbers);  // [2, 3, 4]

Case 2: Setting start and deleteCount

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(2, 2);
console.log(numbers);  // [0, 1, 4]
console.log(removedNumbers);  // [2, 3]

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(-3, 2);
console.log(numbers);  // [0, 1, 4]
console.log(removedNumbers);  // [2, 3]

Case 3: Setting start, deleteCount, and items

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(2, 2, 'item1', 'item2');
console.log(numbers);  // [0, 1, "item1", "item2", 4]
console.log(removedNumbers);  // [2, 3]

const numbers = [0, 1, 2, 3, 4];
const removedNumbers = numbers.splice(-3, 2, 'item1', 'item2');
console.log(numbers);  // [0, 1, "item1", "item2", 4]
console.log(removedNumbers);  // [2, 3]

Reference

MDN Docs