String split and get first and last occurrences

Question

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\'\";

Answer 1

If you're really getting a performance problem from the large array (dont' optimize prematurely), you could use slice to extract the single strings and indexOf/lastIndexOf to find their positions:

str.slice(0, str.indexOf(','))
and
str.slice(str.lastIndexOf(',')+1) // 1==','.length

Answer 2

There is jsperf using substr / substring that is the most optimal way. See:

https://jsperf.com/slice-vs-substr-vs-substring-vs-split-vs-regexp

Answer 3

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];

Answer 4

I have a long string of ISO dates

Assuming these are all using timezone Z, year >= 0 and are spaced and quoted the same way, you don't even have to search for , because they will be of the same length.

var first = str.slice(1, 25),
    last = str.slice(-25, -1);