Append an Item at the End of an Array in JavaScript or Node.js

Arrays are a commonly used data structure in JavaScript applications. Arrays represent a list of items that you can manipulate to your own needs. You can add new items to an existing array with ease.

This tutorial shows you three ways of appending new items to the end of an existing array.

Node.js Series Overview

  1. String Replace All Appearances
  2. Remove All Whitespace From a String in JavaScript
  3. Generate a Random ID or String in Node.js or JavaScript
  4. Remove Extra Spaces From a String in JavaScript or Node.js
  5. Remove Numbers From a String in JavaScript or Node.js
  6. Get the Part Before a Character in a String in JavaScript or Node.js
  7. Get the Part After a Character in a String in JavaScript or Node.js
  8. How to Check if a Value is a String in JavaScript or Node.js
  9. Check If a String Includes All Strings in JavaScript/Node.js/TypeScript
  10. Check if a Value is a String in JavaScript and Node.js
  11. Limit and Truncate a String to a Given Length in JavaScript and Node.js
  12. Split a String into a List of Characters in JavaScript and Node.js
  13. How to Generage a UUID in Node.js
  14. Reverse a String in JavaScript or Node.js
  15. Split a String into a List of Lines in JavaScript or Node.js
  16. Split a String into a List of Words in JavaScript or Node.js
  17. Detect if a String is in camelCase Format in Javascript or Node.js
  18. Check If a String Is in Lowercase in JavaScript or Node.js
  19. Check If a String is in Uppercase in JavaScript or Node.js
  20. Get the Part After First Occurrence in a String in JavaScript or Node.js
  21. Get the Part Before First Occurrence in a String in JavaScript or Node.js
  22. Get the Part Before Last Occurrence in a String in JavaScript or Node.js
  23. Get the Part After Last Occurrence in a String in JavaScript or Node.js
  24. How to Count Words in a File
  25. How to Shuffle the Characters of a String in JavaScript or Node.js
  26. Append Characters or Words to a String in JavaScript or Node.js (Coming soon)
  27. Check if a String is Empty in JavaScript or Node.js (Coming soon)
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js (Coming soon)
  29. Left-Trim Characters Off a String in JavaScript or Node.js (Coming soon)
  30. Right-Trim Characters Off a String in JavaScript or Node.js (Coming soon)
  31. Lowercase the First Character of a String in JavaScript or Node.js (Coming soon)
  32. Uppercase the First Character of a String in JavaScript or Node.js (Coming soon)
  33. Prepend Characters or Words to a String in JavaScript or Node.js (Coming soon)
  1. Get Number of Seconds Since Epoch in JavaScript
  2. Get Tomorrow’s Date in JavaScript
  3. Increase a Date in JavaScript by One Week
  4. Add Seconds to a Date in Node.js and JavaScript
  5. Add Month(s) to a Date in JavaScript or Node.js
  6. Add Week(s) to a Date in JavaScript or Node.js
  7. Get the Current Year in JavaScript or Node.js
  8. How to Get a UNIX Timestamp in JavaScript or Node.js
  9. How to Convert a UNIX Timestamp to a Date in JavaScript or Node.js
  10. Add Days to a Date in JavaScript or Node.js
  11. Get Yesterday's Date in JavaScript or Node.js
  12. Add Minutes to a Date in JavaScript or Node.js (Coming soon)
  13. Add Hours to a Date in JavaScript or Node.js (Coming soon)
  14. Check If a Date Is Today in JavaScript or Node.js (Coming soon)
  15. Check If a Date is Tomorrow in JavaScript or Node.js (Coming soon)
  16. Check If a Date is Yesterday in JavaScript or Node.js (Coming soon)
  17. How to Format a Date YYYY-MM-DD in JavaScript or Node.js (Coming soon)

3 Ways Adding Items to the End of a JavaScript Array

JavaScript comes with the Array#push method allowing you to push one or more items to the end of the array. You may also append new items by creating a new array using the spread operator to push existing items to the beginning. Another way is the concatenation of arrays creating a new one.

Let’s explore all options in the paragraphs below.

Push Items Into an Existing Array

The Array#push method appends one or more items to the end of the array.

*Notice: Array#push changes the values of the array, but doesn’t return the array with the newly added items. It returns the new array length:

const ids = [1, 2, 3]

const newArrayLength = ids.push(4)  
// 4
// the value of "ids" is [1, 2, 3, 4]

// or push multiple values

ids.push(5, 6, 7)  
// the value of "ids" is [1, 2, 3, 4, 5, 6, 7]

Spread and Append Items Into a New Array

You can also create a new array containing existing and new items. Create a new array and use the spread operator to add all items of an existing array to the beginning of the new array. Then, add all new items at the end:

const ids = [1, 2, 3]

const newIds = [...ids, 4]  
// [1, 2, 3, 4]

const newIds = [...ids, 4, 5, 6]  
// [1, 2, 3, 4, 5, 6]

Concat(enate) Items to an Array

Another idea is to concatenate existing and new items to a new array. Here you must concatenate new items onto the existing array. That keeps the order of appending new items to the end:

const ids = [1, 2, 3]

const newIds = ids.concat(4, 5, 6)  
// the value of "newIds" is [1, 2, 3, 4, 5, 6]

That’s it! All three ways allow you to append one or more items to the end of a JavaScript array.

What Should You Use?

Well, use what you like best!

I prefer Array#concat when building an array pipeline by chaining further operations, like Array#map, Array#filter, or Array#find.

In situations where I only want to append the item without additional operations, I’m using the spread operator.

In terms of performance: I don’t really care about performance optimizations on my side. I’m relying on the JavaScript runtime to optimize the code for me. This gives me the freedom of writing the code I like to read 😃

Explore the Library

Find interesting tutorials and solutions for your problems.