TypeScript - insert many elements to array

In TypeScript it is not intuitive at first time how to insert elements to array starting from some index position. The insert operation can be achieved with Array.prototype.splice method. This article is focused on how to do it.

1. Insert elements starting from some index position with Array.prototype.splice method example

// ONLINE-RUNNER:browser;

//           index:       0    1    2    3
const array: string[] = ['a', 'b', 'c', 'd'];

// inserting into 1st index position, 1 element, 'new item' element
array.splice(1, 0, 'new item 1', 'new item 2', 'new item 3', 'new item N');

console.log(array);

Output:

[
  'a',
  'new item 1',
  'new item 2',
  'new item 3',
  'new item N',
  'b',
  'c',
  'd'
]

Notes about Array.prototype.splice method:

• takes as first argument index into 1st index position
• takes as second argument number of removed elements - in this case we do not remove elements
• takes as third and next arguments elements that will be added - number of elements is not limited