Regular expression to count number of commas in a string

Question

How can I build a regular expression that will match a string of any length containing any characters but which must contain 21 commas?

Answer 1

var valid = ((" " + input + " ").split(",").length == 22);

or...

var valid = 21 == (function(input){
    var ret = 0;
    for (var i=0; i

Will perform better than...

var valid = (/^([^,]*,){21}[^,]*$/).test(input);