jQuery password strength checker

The best way is to take an existing plugin as TJB suggested.

As to your question about the code itself, a nicer way is to write it like that:

var pass = "f00Bar!";

var strength = 1;
var arr = [/.{5,}/, /[a-z]+/, /[0-9]+/, /[A-Z]+/];
jQuery.map(arr, function(regexp) {
  if(pass.match(regexp))
     strength++;
});

(Modified to correct syntax errors.)