Create comma-delimited string

Array.prototype.join() is what you’re looking for:

arr.join(',');

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/join

var arr = ['Hi', 'I', 'am', 'a', 'comma', 'separated', 'list'];

arr.join(',');  // === "Hi,I,am,a,comma,separated,list"