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.

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 ?

I do it to avoid having to match all the quotes of the in the array declartion. — Subir Kumar Sao
– Subir Kumar Sao, Commented Jan 30, 2013 at 12:24
This doesn't belong on Stack Overflow. A short answer though: minification. These libraries are squeezed into minified versions with minimal whitespace and short variable names. As it turns out, splitting is shorter (in characters) than writing a array literal. — Mattias Buelens
– Mattias Buelens, Commented Jan 30, 2013 at 12:25
@MattiasBuelens Struggling to see how it isn't on topic for SO. — lonesomeday
– lonesomeday, Commented Jan 30, 2013 at 12:27

Cerbrus · Accepted Answer · 2013-01-30 12:36:16Z

15

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

edited Jan 30, 2013 at 12:36

answered Jan 30, 2013 at 12:26

Cerbrus

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3 Comments

Dreen Over a year ago

Its still surprising to see that on average its better to waste time on computation rather than downloading the source. I would have thought the opposite.

Cerbrus Over a year ago

@Dreen, think of it this way: Considering the MASSIVE amount of jQuery users, for more popular libraries, every byte matters. (So, this is more a server-side optimisation, than client-side)

JJJ Over a year ago

@Dreen A bit late to the party, but based on the linked jsperf, on my computer the slower method is only 0.000005 milliseconds slower. Not only is the "waste" negligible, but even the fastest internet connection won't download one byte of data in that time so on the whole it's still faster.

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