Using string split instead of array declaration array with substrings

Question

I often notice when people split a string of substrings instead of just declare an array of the necessary strings.

Example in moment.js:

langConfigProperties = 'months|monthsShort|weekdays|weekdaysShort|weekdaysMin|longDateFormat|calendar|relativeTime|ordinal|meridiem'.split('|'),

Example in jQuery

 "Boolean Number String Function Array Date RegExp Object".split(" ")

What is a reason to prefer such way ?

Answer 1

It's way slower to use the .split, but it has the advantage that the code can be shorter (Less characters):

var array = 'months|monthsShort|weekdays|weekdaysShort|weekdaysMin|longDateFormat|calendar|relativeTime|ordinal|meridiem'.split('|');
var array = ['months','monthsShort','weekdays','weekdaysShort','weekdaysMin','longDateFormat','calendar','relativeTime','ordinal','meridiem'];

In this example, the difference isn't huge, but if you have 100 variables, the difference gets more significant.

The length added by the delimiter in the split version is 11 + 1 * n, where n is the number of elements, the 11 is for the .split('|')
For the array version, that's 2 + 3 * (n - 1), the 2 for the [].

That means that as soon as you have 6 elements, the .split version is shorter:

for(var i = 5; i < 8; i++){
    console.log('Elements:', i, 'split:', 11 + (i-1), 'array:', 2 + 3 * (i-1));
}
// Elements: 5 split: 15 array: 14
// Elements: 6 split: 16 array: 17
// Elements: 7 split: 17 array: 20