JavaScript - insert element to array

In JavaScript, it is not intuitive to insert an element to an array into some index position. Insert an element into some index position operation can be achieved with Array.prototype.splice method. This article is focused on how to do it.

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//  index:    0    1    2    3

var array = ['a', 'b', 'c', 'd'];

​

// inserting 'new item' element into 1st index position

array.splice(1, 0, 'new_item');

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console.log(array);

Output:

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[ 'a', 'new_item', '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 argument added element

1. Array.prototype.splice method - MDN Docs