Javscript match error - Invalid quantifer

Question

Hi,
i get an strange error "invalid quantifer" ... can somebody help me please?

html

<input type="text" value="5+5" id="test"/>

JS

  ups = {};
  ups['2'] = new Array();
  ups['2']['cmd'] = '#(\-|\+|\*|\/|)[0-9](,|[0-9]|)(\-|\+|\*|\/)[0-9]#gi';     

  var inp_val = $('#test').val();
  if (inp_val.match(ups['2']['cmd']))
  {
     $('body').append('<br />OK');                 
  }

http://www.jsfiddle.net/V9Euk/639/

Thanks in advance!
Peter

Answer 1

In Javascript, Regular expressions should be written as

var re = /thepatterns/mod;

i.e.

  ups = {};
  ups['2'] = new Array();
  ups['2']['cmd'] = /(\-|\+|\*|\/|)[0-9](,|[0-9]|)(\-|\+|\*|\/)[0-9]/gi;     

moreover, it can be simplified as

  ups = {2: {cmd: /([-+*\/])\d([,\d]?)([-+*\/])\d/g }};

---

The reason for the invalid quantifier is that, unlike PHP, a \ followed by an unrecognized character will result in that character without the \:

• Javascript '\p\q' == 'pq'
• PHP '\p\q' == '\\p\\q'

Therefore, your string will be interpreted as

'#(-|+|*|/|)[0-9](,|[0-9]|)(-|+|*|/)[0-9]#gi'

which is an invalid regex since the + (a quantifier) is not preceded by any patterns.