JavaScript String Replace Regex with Examples and Tips

JavaScript plays an important role in creating interactive and engaging websites. One of its dynamic features is the ability to manipulate JavaScript String Replace Regex, a fundamental aspect of programming.

The “JavaScript string replace regex” method offers developers with a functional tool for replacing specific patterns within strings using regular expressions.

What is JavaScript String Replace?

JavaScript string replace is a method that enables you to replace circumstances of a specified substring or pattern within a string with a new substring.

Regular expressions, usually simplified as “regex“, improved this functionality by allowing you to perform advanced pattern matching and replacement.

Syntax of the replace() Method

The syntax of the replace() method is the following:

string.replace(searchValue, newValue);

  • string
    • The initial string that you want to employ.
  • searchValue
    • The substring or regular expression pattern to be replaced.
  • newValue
    • The new substring will replace the matched pattern.

Example Usage

Let’s take a look at the following example:

const originalStringValue = "Welcome, Itsourcecode!";
const newStringValue = originalStringValue.replace("World", "Universe");

Advanced String Replacement using Regular Expressions

Utilizing the Power of Regular Expressions

Regular expressions provide a more flexible and powerful method to string replacement.

They enable you to define complicated patterns for matching, making it possible to replace multiple circumstances of a specific pattern in a single operation.

Using Regular Expressions in replace()

To use regular expressions with the replace() method, you need to provide a regular expression as the search value.

For example, to replace all circumstances of the word “diego” regardless of case, you can use the following code.

const person = "My name is Diego.";
const result = person.replace(/diego/gi, "Regor");


My name is Regor.

Common Use Cases and Practical Examples

URL Cleanup using Regular Expressions

Generally, web developers need to sanitize URLs by eliminating unimportant query parameters.

By using regular expressions in combination with the replace() method.

Here’s an example code:

const regularURL = "";
const result = regularURL.replace(/(\?|&)param\d+=\w+/g, "");

Formatting Numbers with Commas

Formatting numbers with commas is a typical requirement in web applications.

Here’s an example code how you can obtain this using regex and the replace() method:

const numberWithCommasValue = "300000000";
const result = numberWithCommasValue.replace(/\B(?=(\d{3})+(?!\d))/g, ",");


Can I use variables in the replacement string?

Yes, you can use variables in the replacement string.

Is the replace() method case-sensitive?

By default, the replace() method is case-sensitive. However, you can make it case-insensitive by using the I flag with regular expressions.


In web development, mastering string manipulation is very important, and the JavaScript replace() method combined with regular expressions opens up a realm of possibilities.

This article has provided you with an in-depth understanding of how to use this method to its fullest potential.

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