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

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.

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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!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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