regex - Range out of order in character class in javascript

Question

I don't know why my regex is incorrect:

var domain = "google.com.br";
var reEmail = new RegExp("^([A-Za-z0-9_-.])+@" + domain + "$");

I need this to validate an email. Example below: reEmail.test("contact@google.com.br");

I get this error:

Range out of order in character class

Answer 1

Because you create the RegExp using a String the _-. becomes _-. and that is the invalid range. (It is a range from _ to . and that is not correct)

You need to double escape it:

new RegExp("^([A-Za-z0-9_\-\.])+@" + domain + "$");

That way the \ becomes a in the String and then is used to escape the -in the RegExp.

EDIT:

If you create RegExp by String it is always helpful to log the result so that you see if you did everything right:

e.g. your part of the RegExp

console.log("^([A-Za-z0-9_-.])+@");

results in:

^([A-Za-z0-9_-.])+@