Question

So for example:

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

But this is of course not working 🙂
Is there any way to do this?

Answer 1

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

Update

Per some of the comments, it’s important to note that you may want to escape the variable if there is potential for malicious content (e.g. the variable comes from user input)

ES6 Update

In 2019, this would usually be written using a template string, and the above code has been updated. The original answer was:

var regex = new RegExp("ReGeX" + testVar + "ReGeX");
...
string.replace(regex, "replacement");