alpha-sortable

Encode/decode numbers in strings so that they sort properly

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?

1. Zero-pad to a reasonable amount -- like how big you think things will probably get in the life of the system
2. When you get bigger numbers, prefix them with a flagged length that keeps them sorting properly. The flag is an 'E' for every digit in the length counter, followed by the length counter, followed by a hyphen.

A few examples (more below):

Number	Encoded with default setting {length: 4}
1	0001
10	0010
100	0100
1000	1000
10000	E5-10000
100000000	E9-100000000
1000000000	EE10-1000000000
1e+100	EEE101-10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

API

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

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

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

console.log(stringify(20000000))
// => E8-20000000

console.log(parse('E8-20000000') === 20000000)
// true

More Examples

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

Number	BigInt	encoded {length: 4}
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	E5-10000
99999	99999n	E5-99999
100000	100000n	E6-100000
999999	999999n	E6-999999
1000000	1000000n	E7-1000000
9999999	9999999n	E7-9999999
10000000	10000000n	E8-10000000
99999999	99999999n	E8-99999999
100000000	100000000n	E9-100000000
999999999	999999999n	E9-999999999
1000000000	1000000000n	EE10-1000000000
9999999999	9999999999n	EE10-9999999999
10000000000	10000000000n	EE11-10000000000
99999999999	99999999999n	EE11-99999999999
100000000000	100000000000n	EE12-100000000000
999999999999	999999999999n	EE12-999999999999
1000000000000	1000000000000n	EE13-1000000000000
9999999999999	9999999999999n	EE13-9999999999999
10000000000000	10000000000000n	EE14-10000000000000
99999999999999	99999999999999n	EE14-99999999999999
100000000000000	100000000000000n	EE15-100000000000000
999999999999999	999999999999999n	EE15-999999999999999
1000000000000000	1000000000000000n	EE16-1000000000000000
10000000000000000	9999999999999999n	EE16-9999999999999999
10000000000000000	10000000000000000n	EE17-10000000000000000
100000000000000000	99999999999999999n	EE17-99999999999999999
100000000000000000	100000000000000000n	EE18-100000000000000000
1000000000000000000	999999999999999999n	EE18-999999999999999999
1000000000000000000	1000000000000000000n	EE19-1000000000000000000
10000000000000000000	9999999999999999999n	EE19-9999999999999999999
10000000000000000000	10000000000000000000n	EE20-10000000000000000000
100000000000000000000	99999999999999999999n	EE20-99999999999999999999
100000000000000000000	100000000000000000000n	EE21-100000000000000000000
1e+21	999999999999999999999n	EE21-999999999999999999999
1e+21	1000000000000000000000n	EE22-1000000000000000000000
1e+22	9999999999999999999999n	EE22-9999999999999999999999
1e+22	10000000000000000000000n	EE23-10000000000000000000000
1e+23	99999999999999999999999n	EE23-99999999999999999999999
1e+23	100000000000000000000000n	EE24-100000000000000000000000
1e+24	999999999999999999999999n	EE24-999999999999999999999999
1e+24	1000000000000000000000000n	EE25-1000000000000000000000000
1e+25	9999999999999999999999999n	EE25-9999999999999999999999999
1e+25	10000000000000000000000000n	EE26-10000000000000000000000000

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 'E' 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 'E'

A. It has to be a character that sorts after 9, which is most of them. Since the notation is very similar to scientific notation, 'E' seemed like a good idea. We also want it to be a character that's going to be legal in pretty much every context, including URLs. 'E' and hyphen seem to pass that test.

Q. Does the 'E' have to be uppercase?

A. Let's say yes. We don't have a clear example of where a lowercase E would break something, but it seems like a bad idea.