JavaScript wrong RegEx?

Question

A short question: The following line throws SyntaxError: nothing to repeat

var regexTel = new RegExp('\+[0-9 ]+');

Tools like http://www.regexpal.com/ says that the pattern works fine.

Answer 1

Remember that \ is special in string literals as well as in regular expressions, so a single \ in a string literal escapes what follows it at the string level; so your regex doesn't actually have that \ in it at all. (Since \+ is meaningless in a string literal, it's handled as simpley +.) You'd need to escape it at the string level with another backslash:

var regexTel = new RegExp('\\+[0-9 ]+');

But, in JavaScript, you don't have to use strings; use a regex literal instead, so you don't have that problem:

var regexTel = /\+[0-9 ]+/;

Answer 2

If what you want is repeat a backslash \, you need to escape it:

var regexTel = new RegExp('\\+[0-9 ]+');

Answer 3

As others point out, it's either to add the slashes in the string you pass to the regex:

var regexTel = new RegExp('/\+[0-9 ]+/');

Or either use the more compact version that removes the use of the RegExp object:

var regexTel = /\+[0-9 ]+/;

Answer 4

You have to escape "+" sign. In your regex "\" sign is recognized as a delimiter. Go with:

var regexTel = new RegExp(/\+[0-9 ]+/);

Answer 5

try this

var regexTel = new RegExp(/\+[0-9 ]+/);