Talk:Core JavaScript 1.5 Reference:Global Objects:Array:join

From MDC

Here is a compatibility note with Array.join (and String.split) that when given an argument of undefined in older versions of JS, it is converted to the string 'undefined'. I'm not sure which version of JS fixed this.

eg:

 [1,2,3].join(undefined) == "1undefined2undefined3"  // not ECMA compliant
 [1,2,3].join() == "1,2,3"