How can I add new array elements at the beginning of an array in Javascript?

Question

How can I add new array elements at the beginning of an array in Javascript?

I have a need to add or prepend elements toward the start of an array.

For instance, if my array looks like beneath:

[23, 45, 12, 67]

And the response from my AJAX call is 34, I want the updated array to be like the following:

[34, 23, 45, 12, 67]

Currently, I am preparing to do it like this:

var newArray = [];

newArray.push(response);



for (var i = 0; i < theArray.length; i++) {

    newArray.push(theArray[i]);

}



theArray = newArray;

delete newArray;

Is there any better way to do this? Does Javascript have any built-in functionality that does this?

array javascript

3 years ago by Kajalsi45d

2 Answers

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**aashaykumar** · Answer 1 · 2021-06-02T10:11:36

aashaykumar



var arr = [23, 45, 12, 67];

arr = [34, ...arr]; // RESULT : [34,23, 45, 12, 67]



console.log(arr)

3 years ago

**RoliMishra** · Answer 2 · 2021-06-03T14:00:57

Another way to do that through concat

var arr = [1, 2, 3, 4, 5, 6, 7];

console.log([0].concat(arr));

The difference between concat and unshift is that concat returns a new array. The performance between them could be found here.

function fn_unshift() {

  arr.unshift(0);

  return arr;

}



function fn_concat_init() {

  return [0].concat(arr)

}

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How can I add new array elements at the beginning of an array in Javascript?

2 Answers

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