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Node.js — String Replace All Appearances

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String replacements are a common task in app development. JavaScript has powerful string methods and you intentionally think of string.replace() when reading the headline. Good catch, but there’s a trick to replacing all appearances when using it. Read on to get the details!

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String.replace(): One Appearance

Imagine the following example: you have a string that includes dashes, like a UUID. Now you want to remove all dashes in this string. A way to go is replacing all dashes with an empty string.

Now you may go ahead and use string.replace('-', ''). The problem: it replaces only the first dash because the method searches for the substring“-” and stops when found. It won’t replace the second, third, and other dashes in the string.

const string = 'e851e2fa-4f00-4609-9dd2-9b3794c59619'

console.log(string.replace('-', ''))  
// -> e851e2fa4f00-4609-9dd2-9b3794c59619

The next section describes you how to replace all dash appearances in the string.

String.replace(): Replace All Appearances

A regular expression instead of a string will replace all appearances. Pass it in as the first argument to string.replace():

const string = 'e851e2fa-4f00-4609-9dd2-9b3794c59619'

console.log(string.replace(/-/g, ''))  
// -> e851e2fa4f0046099dd29b3794c59619

As you can see, using a string as the substring to search for will only replace the first appearance. A regular expression with the /g suffix replaces all dashes with an empty string.

Using a Variable

You should create a RegEx when using dynamic values as the search string. JavaScript provides a RegExp class to create a regular expression based on your variables:

const search = '-`  
const replacer = new RegExp(search, 'g')

const string = 'e851e2fa-4f00-4609-9dd2-9b3794c59619'

console.log(string.replace(replacer, '/'))  
// -> e851e2fa/4f00/4609/9dd2/9b3794c59619

Enjoy coding & make it rock!

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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