How do I include variables in regular expressions in JavaScript?

Include Variables in Regular Expressions in JavaScript

In JavaScript, using a variable as part of a regular expression can be achieved by creating a new RegExp object with the variable embedded within the pattern.

Consider the following example:

function(input) {
    var testVar = input;
    string = ...
}

To include testVar in the regex, a new RegExp object should be created:

const regex = new RegExp(`ReGeX${testVar}ReGeX`);
...
string.replace(regex, "replacement");

This creates a regular expression object with the variable's value incorporated into the pattern.

Note: If the variable contains user input or can potentially contain malicious content, it's essential to escape the variable using escape() to prevent security vulnerabilities.

Update (2019):

Modern JavaScript development often employs template literals for string interpolation. Here's an updated version of the example using template literals:

function(input) {
    var testVar = input;
    string = ...
}
...
string.replace(/ReGeX${testVar}ReGeX/, "replacement");

This method leverages template literals to dynamically construct the regular expression pattern, effectively achieving the desired result.

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