Replace Multiple Characters in a String using JavaScript

Replace Multiple Characters in a String #

Use the replace() method to replace multiple characters in a string, e.g. str.replace(/[._-]/g, ' '). The first parameter the method takes is a regular expression that can match multiple characters. The method returns a new string with the matches replaced by the provided replacement.

index.js

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const str = 'one.two_three-four';

const result1 = str.replace(/[._-]/g, ' ');
console.log(result1); // 👉️ "one two three four"

// ✅️ without regular expressions
const result2 = str
  .replaceAll('.', '?')
  .replaceAll('_', '?')
  .replaceAll('-', '?');

console.log(result2); // 👉️ "one?two?three?four"

We passed the following 2 parameters to the String.replace method:

a regular expression we want to match in the string
the replacement for each match

The forward slashes / / mark the beginning and end of the regular expression.

The square brackets [] are called a character class and match any of the characters between the brackets. In the first example, we match a dot, underscore and a hyphen.

You can adapt the regular expression to your use case, by updating the characters in the square brackets and the replacement string.

We used the g (global) flag, because we want to match all occurrences of these characters in the string, and not just the first occurrence.

In the first example, we replace each occurrence of a dot, underscore or hyphen with a space.

The replace method does not change the original string, it returns a new string. Strings are immutable in JavaScript.

If you ever need help reading a regular expression, check this regex cheatsheet from MDN out.

Replace Multiple Characters in a String using replaceAll #

The second example shows how to use the String.replaceAll to achieve the same result.

To replace multiple characters in a string, chain multiple calls to the replaceAll() method, e.g. str.replaceAll('.', '!').replaceAll('_', '!'). The replaceAll method will return a new string, where all occurrences of the characters are replaced by the provided replacement.

index.js

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const str = 'one.two_three-four';

// 👇️ without regular expressions
const result2 = str
  .replaceAll('.', '?')
  .replaceAll('_', '?')
  .replaceAll('-', '?');

console.log(result2); // 👉️ "one?two?three?four"

We passed the following 2 parameters to the replaceAll method:

A substring we want to replace in the string
The replacement for each match

This approach is a bit more verbose then using a regular expression with a character class, however it allows us to avoid using a regular expression if we have specific characters we want to replace.

The difference in performance is most likely negligible, unless you're working with a string that's tens of thousands of characters long.

The replaceAll method returns a new string where the character is replaced by the provided replacement. This allows us to chain as many calls to the method as necessary.

An alternative but also very common approach you might see is using a pipe | character, which serves as an or in regular expressions.

Here's an example that replaces each whitespace, underscore or exclamation mark with a question mark.

index.js

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const str = 'one two_three!four';
const result3 = str.replace(/\s|_|!/g, '?');

console.log(result3); // 👉️ "one?two?three?four"

The \s special character matches a whitespace (spaces, tabs, newlines).

The pipe | allows us to match either one of the characters in the regex.

Which approach you pick is a matter of personal preference. I'd go with the character class [] and replace method approach if the team I'm on is comfortable with regular expressions. Otherwise, I'd probably chain calls to the replaceAll method.

Replace Multiple Characters in a String using JavaScript