I have a long string of ISO dates:
var str = \"\'2012-11-10T00:00:00.000Z\', \'2012-11-11T00:00:00.000Z\', **** \'2013-11-12T00:00:00.000Z\'\";
It's really not a waste of space, since Javascript is barely taking up any memory on the computer. Unless the string is gigabytes long, I wouldn't worry about it. To get the first and last, just do this:
arr=str.split(',');
var first=arr.shift(); //or arr[arr.length-1];
var last=arr.pop(); //or arr[0];