alpha-sortable

Encode/decode numbers in strings so that they sort properly

Note: I had not heard of natural sort order when I wrote this. This is a rather different approach. Should be revisited with an eye to Alphanum.

Why?

Because sometimes you want items sorted in numeric order, even though they are sorted on a text field. Example: filenames.
Zero padding only works if your users are okay with lots of zeros, and/or you know your numbers will never get large.

How?

Zero-pad to a reasonable amount -- like how big you think things will probably get in the life of the system
When you get bigger numbers, prefix them with a flagged length that keeps them sorting properly. The flag is a "=" for every digit in the length counter, followed by the length counter, followed by an underscore.
Negative integers down to Number.MIN_SAFE_INTEGER are serialized as "-M+" followed by the number minus Number.MIN_SAFE_INTEGER

A few examples (more below):

Number	Encoded with default setting {length: 4}
1	0001
10	0010
100	0100
1000	1000
10000	=5-10000
100000000	=9-100000000
1000000000	==10-1000000000
1e+100	===101-10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

API

import {stringify, parse} from 'alpha-sortable'

console.log(stringify(20))
// => 0020

console.log(stringify(20, {length: 2}))
// => 20

console.log(stringify(20000000))
// => =8-20000000

console.log(parse('=8-20000000') === 20000000)
// true

More Examples

Here's the full output of demo-table.js :

Number	BigInt	encoded {length: 4}
-3	-3n	-M+9007199254740988
-2	-2n	-M+9007199254740989
-1	-1n	-M+9007199254740990
0	0n	0000
1	1n	0001
9	9n	0009
10	10n	0010
99	99n	0099
100	100n	0100
999	999n	0999
1000	1000n	1000
9999	9999n	9999
10000	10000n	=5_10000
99999	99999n	=5_99999
100000	100000n	=6_100000
999999	999999n	=6_999999
1000000	1000000n	=7_1000000
9999999	9999999n	=7_9999999
10000000	10000000n	=8_10000000
99999999	99999999n	=8_99999999
100000000	100000000n	=9_100000000
999999999	999999999n	=9_999999999
1000000000	1000000000n	==10_1000000000
9999999999	9999999999n	==10_9999999999
10000000000	10000000000n	==11_10000000000
99999999999	99999999999n	==11_99999999999
100000000000	100000000000n	==12_100000000000
999999999999	999999999999n	==12_999999999999
1000000000000	1000000000000n	==13_1000000000000
9999999999999	9999999999999n	==13_9999999999999
10000000000000	10000000000000n	==14_10000000000000
99999999999999	99999999999999n	==14_99999999999999
100000000000000	100000000000000n	==15_100000000000000
999999999999999	999999999999999n	==15_999999999999999
1000000000000000	1000000000000000n	==16_1000000000000000
10000000000000000	9999999999999999n	==16_9999999999999999
10000000000000000	10000000000000000n	==17_10000000000000000
100000000000000000	99999999999999999n	==17_99999999999999999
100000000000000000	100000000000000000n	==18_100000000000000000
1000000000000000000	999999999999999999n	==18_999999999999999999
1000000000000000000	1000000000000000000n	==19_1000000000000000000
10000000000000000000	9999999999999999999n	==19_9999999999999999999
10000000000000000000	10000000000000000000n	==20_10000000000000000000
100000000000000000000	99999999999999999999n	==20_99999999999999999999
100000000000000000000	100000000000000000000n	==21_100000000000000000000
1e+21	999999999999999999999n	==21_999999999999999999999
1e+21	1000000000000000000000n	==22_1000000000000000000000
1e+22	9999999999999999999999n	==22_9999999999999999999999
1e+22	10000000000000000000000n	==23_10000000000000000000000
1e+23	99999999999999999999999n	==23_99999999999999999999999
1e+23	100000000000000000000000n	==24_100000000000000000000000
1e+24	999999999999999999999999n	==24_999999999999999999999999
1e+24	1000000000000000000000000n	==25_1000000000000000000000000
1e+25	9999999999999999999999999n	==25_9999999999999999999999999
1e+25	10000000000000000000000000n	==26_10000000000000000000000000

FAQ

Q. Isn't there some standard way to do this?

A. Not that I could find.

Q. Is there a maximum number it can handle?

A. No. For example, it could handle a googolplex by starting with a googol '=' characters. No problem! (Of course, no computer in this universe will ever be able to hold a number as large as a googolplex.)

Q. Why '='

A. We want it to sort between the numbers and the words, so that means ":;<=>?@" are the options. "<>?" tend to be meta-characters. Among ":;=@", "=" seemed the most number-related, and the least likely to be a metacharacter.

Q. Why are negative numbers so ugly and limited?

This was the first thing I thought of.

We could do it as -dd_n where dd is two digit number giving us the offset, as offset = 10**(100-dd). That gets us down to 1e-99 or so, which is pretty good!

-99 => -98_01
-10 => -98_99
-2 => -99_8
-1 => -99_9

sandhawke/alpha-sortable