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How to Escape RegExp Special Characters in Javascript (or Typescript)

Jasser Mark Arioste

Jasser Mark Arioste

How to Escape RegExp Special Characters in Javascript (or Typescript)

This tutorial shows you three ways to escape special characters in query strings.

Why Do you need to escape regex special characters? #

There was an issue in my projects where the user could not find records if the plus(+) symbol was included in the query string. When searching for users/records with the plus symbol included in the email field, the database did not return any results. I used MongoDB as the database and used the $regex operator.

The problem was that the query string was not escaped and MongoDB was interpreting the plus symbol differently. This is because the plus (+) symbol is a special regex character that has to be escaped!

❌ Incorrect query: {email: {$regex: /user+test/, options: "i"}}

✅ Correct query(the plus sign is now escaped!): {email: {$regex: /user\+test/, options: "i"}}

What characters need to be escaped? #

You need to escape all special regex characters so that they will be treated as regular strings. The following is the list of special characters in regex in javascript:

!#$%^&*)(+=.<>{}[]:;'"|~`_-
1

More info here

Using Plain Javascript/Typescript #

 To transform a string to its escaped version, we'll create a regex of all the special characters and use javascript string.replace function. I prefer this method since we don't have to install a package.

const REGEXP_SPECIAL_CHAR =
  /[\!\#\$\%\^\&\*\)\(\+\=\.\<\>\{\}\[\]\:\;\'\"\|\~\`\_\-]/g;

//base query
const queryString = 'user+test@gmail.com';

// prepend a backslash and insert the matched character.
const escapedQuery = query.replace(REGEXP_SPECIAL_CHAR, '\\$&');

console.log(escapedQuery); // user\+test@gmail\.com

//for example if we want to use it in MongoDB:
// db.users.find({
//    email: {$regex: new RegExp(escapedQuery, "i")}
// })
123456789101112131415

Using Lodash #

If you're using lodash in your project, you'll be able to save time by using lodash's escapeRegex function. Lodash is a modern javascript utility library that is still great to use in many projects!

import escapeRegExp from "lodash/escapeRegExp"

const queryString = 'user+test@gmail.com';

const escapedQueryLodash = escapeRegExp(queryString);
console.log(escapedQueryLodash);  // user\+test@gmail\.com
123456

Using escape-string-regexp package #

If you're not using lodash due to its size or don't want to bother with the first method. You can use the escape-string-regexp npm package, it has a very small size and is very good at what it does. It has a very small footprint (256b) and is also written in typescript.

Installation

yarn add escape-string-regexp

# or
npm install escape-string-regexp
1234

Usage

import escapeRegExp from 'escape-string-regexp';

const queryString = 'user+test@gmail.com';
const escaped = escapeRegExp(queryString)
console.log(escaped) //user\+test@gmail\.com
12345

Conclusion #

We were able to learn three different ways to escape special regexp characters in javascript. 

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Resources #


Credits: Image by David Mark from Pixabay

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