How Can I Use Variables in JavaScript Regular Expressions?

Using Variables in Regular Expression Patterns

In JavaScript, you may find yourself in a situation where you want to use a variable in a regular expression pattern, such as when defining a String.replaceAll() method. While a simple string replacement can be done as shown below:

"ABABAB".replace(/B/g, "A");

To incorporate a variable into the pattern, we need to create a new RegExp object, effectively separating the pattern from the string. Here's how to do it:

const re = new RegExp(`\s${variable}\s`, "g");

This creates a regular expression object that can then be used for replacement:

"mystring1".replace(re, "newstring");

This is particularly useful in situations where you need dynamic patterns or want to reuse the same expression with different variables.

For browsers or Node.js versions that don't support template literals, you can use the following syntax:

const re = new RegExp("\s" + variable + "\s", "g");
"mystring1".replace(re, "newstring");

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