Regex inside `if` check

Question

I'm trying to use regex inside if. Strange, but it doesn't work. How it may be fixed?

It works:

var lang = 'lang-js';
if (lang == 'lang-js') {
  alert('ok');
}

It works too (just for testing purposes):

var lang = 'lang-js';
if (lang == 'lang-' + 'js') {
  alert('ok');
}

But this one doesn't work:

var lang = 'lang-js';
if (lang == 'lang-' + /[a-z]/) {
  alert('not ok');
}

Type `'lang-' + /[a-z]/` in the browser console and see what happens. You're not doing a regular expression test, you are concatenating a regex with a string, which produces a string, and then comparing that with another string. This has nothing to do with jQuery so I've removed that tag. — nnnnnn, Mar 01 '17 at 01:54
http://stackoverflow.com/questions/6603015/check-whether-a-string-matches-a-regex — buræquete, Mar 01 '17 at 01:55

score 5 · Accepted Answer · answered Mar 01 '17 at 01:55

5

use something like this

if (/^lang-[a-z]/.test(lang)) {

you might have to adjust the regex as this just looks for one char.

answered Mar 01 '17 at 01:55

Daniel A. White

score 0 · Answer 2 · answered Mar 01 '17 at 02:06

0

its because typeof /[a-z]/ == 'object' and where ''+/[a-z]/ working toString and your result will be string lang-/[a-z]/

answered Mar 01 '17 at 02:06

MypKOT-1992

2 Answers2