How to split a camel case string containing numbers

Question

I have camel cased strings like this:

"numberOf40"
"numberOf40hc"

How can I split it like this?

["number", "Of", "40"]
["number", "Of", "40hc"]

I am using humps to decamelize keys so I can only pass a split regex as option. I am looking for an answer that only uses split function.

My best attempts:

const a = "numberOf40hc"

a.split(/(?=[A-Z0-9])/)
// ["number", "Of", "4", "0hc"]

a.split(/(?=[A-Z])|[^0-9](?=[0-9])/)
// ["number", "O", "40hc"]

Also I don't understand why the f is omitted in my last attempt.

You don't say what the logic is but I think you shouldn't use split for this since the rule is not simple. — Hogan, Mar 15 '21 at 16:02
Does this help? https://stackoverflow.com/questions/18379254/regex-to-split-camel-case — evolutionxbox, Mar 15 '21 at 16:03
@Hogan I'm using the library Humps to decamelize keys and the only option I can use is a `split` regex — adesurirey, Mar 15 '21 at 16:04
@adesurirey -- you are using a javascript library that does not let you execute a lambda on the data -- I doubt it. — Hogan, Mar 15 '21 at 16:22
from the documentation --> "It also accepts a callback which can modify the conversion behavior." https://www.npmjs.com/package/humps — Hogan, Mar 15 '21 at 16:26
@Hogan yes I saw it but I prefer not rewriting the whole logic if I can — adesurirey, Mar 15 '21 at 16:55

The fourth bird · Accepted Answer · 2021-03-15T16:27:29.890

You don't get the f in you last attempt (?=[A-Z])|[^0-9](?=[0-9]) as this part of the last pattern [^0-9] matches a single char other than a digit and will split on that char.

You could also match instead of split

const regex = /[A-Z]?[a-z]+|\d+[a-z]*/g;

[
  "numberOf40",
  "numberOf40hc"
].forEach(s => console.log(Array.from(s.matchAll(regex), m => m[0])));

Using split only, you could use lookarounds with a lookbehind which is gaining more browser support.

const regex = /(?=[A-Z])|(?<=[a-z])(?=\d)/g;

[
  "numberOf40",
  "numberOf40hc"
].forEach(s => console.log(s.split(regex)));

junvar · Answer 2 · 2021-03-15T16:27:13.113

2

const a = "numberOf40hc"

let b = a.split(/(\d+[a-z]*|[A-Z][a-z]*)/).filter(a => a);

console.log(b);

The .filter(a => a) is necessary because split, returns both the left and right side of a matched delimter. E.g. 'a.'.split('.') returns both the left (i.e. 'a') and right (i.e. '') side of '.'.

Per your update regarding the need for compatibility with humps, it seems humps supports customizing the handler:

const humps = require('humps');

let myObj = {numberOf40hc: 'value'};

let decamelizedObj = humps.decamelizeKeys(myObj, key =>
        key.split(/(\d+[a-z]*|[A-Z][a-z]*)/).filter(a => a).join('_'));

console.log(decamelizedObj);

edited Mar 15 '21 at 16:27

answered Mar 15 '21 at 16:04

junvar

11,151
2
30
46

1

He wants the last element to be `40hc` not `hc` – Hogan Mar 15 '21 at 16:05
Thank you but I am using Humps.js to decamelize keys so I can only pass a `split` regex. I am looking for an answer that only uses `split`. I edited my question to be clearer. – adesurirey Mar 15 '21 at 16:12

score 1 · Answer 3 · answered Mar 15 '21 at 16:05

1

Try this:

const splitStr = (str='') =>
  str.split(/([A-Z][a-z]+)/).filter(e => e);
console.log( splitStr("numberOf40") );
console.log( splitStr("numberOf40hc") );

answered Mar 15 '21 at 16:05

Majed Badawi

27,616
4
25
48

Thank you but I am using Humps.js to decamelize keys so I can only pass a `split` regex. I am looking for an answer that only uses `split`. I edited my question to be clearer. – adesurirey Mar 15 '21 at 16:12

How to split a camel case string containing numbers

3 Answers3