Javascript Regex: How to put a variable inside a regular expression? [duplicate]

Answer 1

You can use the RegExp object:

var regexstring = "whatever";
var regexp = new RegExp(regexstring, "gi");
var str = "whateverTest";
var str2 = str.replace(regexp, "other");
document.write(str2);

Then you can construct regexstring in any way you want.

You can read more about it here.

Answer 2

It's only necessary to prepare the string variable first and then convert it to the RegEx.

for example:

You want to add minLength and MaxLength with the variable to RegEx:

function getRegEx() {
    const minLength = "5"; // for exapmle: min is 5
    const maxLength = "12"; // for exapmle: man is 12

    var regEx = "^.{" + minLength + ","+ maxLength +"}$"; // first we make a String variable of our RegEx
    regEx = new RegExp(regEx, "g"); // now we convert it to RegEx

    return regEx; // In the end, we return the RegEx
}

now if you change value of MaxLength or MinLength, It will change in all RegExs.

Hope to be useful. Also sorry about my English.

Answer 3

if you're using es6 template literals are an option...

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