JavaScript — Join an Array of Strings to a Single String Value

All tutorials here at Future Studio carry a list of tags. We’re assigning tags to tutorials for some kind of grouping. Tutorials may belong to different topics and tags are a good use-case for that.

On the server-side we’re using an array of strings for the tags. When displaying them in the frontend, you probably want to link or format the tags to your needs.

This tutorial shows you how to join a string array to a single string in JavaScript.

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
  27. Check if a String is Empty in JavaScript or Node.js
  28. Ensure a String Ends with a Given Character in JavaScript or Node.js
  29. Left-Trim Characters Off a String in JavaScript or Node.js
  30. Right-Trim Characters Off a String in JavaScript or Node.js
  31. Lowercase the First Character of a String in JavaScript or Node.js
  32. Uppercase the First Character of a String in JavaScript or Node.js
  33. Prepend Characters or Words to a String in JavaScript or Node.js
  34. Check if a String is a Number
  35. Convert a String to Buffer

Join an Array of Strings Using JavaScript

JavaScript arrays support a native join method. The join method concatenates all array values using the given separator. The default separator is a comma ',':

const tags = ['JavaScript', 'Node.js', 'Strings']

const result = tags.join()  
// 'JavaScript,Node.js,Strings'

const result = tags.join(', ')  
// 'JavaScript, Node.js, Strings'

Another way to create a single string out of an array of string values is to combine the map and join methods. A chain of array transformations allows you to customize the output.

For example, you may want to append the last item using an , and suffix. You can do this by mapping your values before joining them:

const tags = ['JavaScript', 'Node.js', 'Strings']

const result = tags.map((str, index, array) => {  
  return index < (array.length - 1)
    ? `${str}, `
    : `and ${str}` 
}).join('')

// 'JavaScript, Node.js, and Strings'

Use the @supercharge/arrays Package

I’m the maintainer of the @supercharge/arrays package providing a fluent interface for Array methods. The @supercharge/arrays package comes with a handy Arr#join method (like the native JavaScript array).

The join method returns a string value of all items concatenated. By default, the package concatenates all values using a comma ,. You may provide your own separator as the first argument. The join method supports an optional, second argument which is used to concatenate the last item to the resulting string.

import { Arr } from '@supercharge/arrays'

const tags = ['JavaScript', 'Node.js', 'Strings']

Arr.from(tags).join()  
// 'JavaScript,Node.js,Strings'

Arr.from(tags).join(', ')  
// 'JavaScript, Node.js, Strings'

Arr.from(tags).join(', ', ', and')  
// 'JavaScript, Node.js, and Strings'

The Arr#join method also supports a callback function to give you all options to create the final string:

import { Arr } from '@supercharge/arrays'

Arr.from('JavaScript', 'Node.js', 'Strings').join((str, index, array) => {  
  return index < (array.length - 1)
    ? `${str}, `
    : `and ${str}` 
})
// 'JavaScript, Node.js, and Strings'

Have fun joining string arrays!


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