Question

I just noticed a very strange behaviour. Why does a simple space break all the tests?

rePattern = /^([a-z]+[-_]?){2,}[a-z]$/; 
var test = new Array("jhgfg_hfh-g", "jhg-fg_hfhg", "jhg_fg_hfhg", "jhg_fg_hfhg", "jhg_fghfhg");
for (var i = 0; i < test.length ; i++) {
   x = test[i];
   alert(i + ' : ' + x + ' : ' + rePattern.test( x ));
}

if i change the above to

// notice {2,} => {2, } with an extra space before }
rePattern = /^([a-z]+[-_]?){2, }[a-z]$/;

then everything become false…

thank u

Answer 1

OK, just to have an accepted answer here: it’s because of the extra space. The syntax of regular expressions is strict, you can’t add random whitespace and expect it’ll be ignored. {2, } will match literal {2, }:

/^x{2, }$/.test('x{2, }') === true