JavaScript - insert many elements to array

In JavaScript, it is not intuitive to insert elements to an 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.

In this example, we use Array.prototype.splice method to insert elements starting from some index position.

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//  index:    0    1    2    3

var array = ['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:

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[

  'a',

  'new item 1',

  'new item 2',

  'new item 3',

  'new item N',

  'b',

  'c',

  'd'

]

Notes about Array.prototype.splice method:

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

1. Array.prototype.splice method - MDN Docs