Javascript: Regex to convert a numbered list string to an array of items

Question

I am trying to convert a numbered list into an array of items. This is what I have so far:

let input = `1. This is a text\n    where each item can span over multiple lines\n  1.1 this is another item\n 1.2another item\n  2. that I want to\n    extract each seperate\n    item from\n    3. How can I do that?`;

let regex = /(\d+\.\d+|\d+)\s(.*)/g;
let matches = input.match(regex);
console.log(matches);

This only produces the following output:

"1.1 this is another item"

What I would like is something like this:

"1. This is a text"
"1.1 this is another item"
"1.2another item"
...and so on

Why is it matching only one item out of this string? What am I doing wrong and how can I fix it?

trincot · Accepted Answer · 2024-04-21 18:51:38Z

3

Your regex does not foresee a dot after a number when there is no second number following it. It also requires a space after the number, but you have a case where there is no such space. So make it optional.

Use the s modifier so . also matches newline characters.

If a new item can start on the same line, you'll need a look-ahead to foresee where a match must end.

Suggested correction:

let input = `1. This is a text\n    where each item can span over multiple lines\n  1.1 this is another item\n 1.2another item\n  2. that I want to\n    extract each seperate\n    item from\n    3. How can I do that?`;

let regex = /(\d+\.\d*)\s?(.*?)(?=\d+\.|$)/gs;
let matches = input.match(regex);
console.log(matches);

edited Apr 21, 2024 at 18:51

answered Jul 14, 2022 at 17:22

trincot

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2 Comments

Aman Over a year ago

Thank you! This works on this example, but when I try it on another string such as the one here, it returns a null or just the entire string.

trincot Over a year ago

OK, I see. Updated my answer.

The fourth bird · Accepted Answer · 2022-07-14 18:19:13Z

Another option using a negated character class:

\b\d+\.\D*(?:\d(?!\.)[^.]*)*

Explanation

\b\d+\.\ A word boundary, match 1+ digits and a dot
\D* Optionally match non digits
(?:\d(?!\.)[^.]*)* Optionally match a digit asserting not a dot directly to the right

Regex demo

let input = `1. This is a text\n    where each item can span over multiple lines\n  1.1 this is another item\n 1.2another item\n  2. that I want to\n    extract each seperate\n    item from\n    3. How can I do that?`;

let regex = /\b\d+\.\D*(?:\d(?!\.)[^.]*)*/g;
let matches = input.match(regex);
console.log(matches);

If you want to keep the start of the string into account where the digits and the dot start, you can follow the match by asserting not a digit and dot pattern at the start of the string:

^[^\S\n]*\d+\..*(?:\n(?![^\S\n]*\d+\.).*)*

Regex demo

let input = "1. This is a text with a number 1.2 and 3.\n    where each item can span over multiple lines\n  1.1 this is another item\n 1.2another item\n  2. that I want to\n    extract each seperate\n    item from\n    3. How can I do that?";

let regex = /^[^\S\n]*\d+\..*(?:\n(?![^\S\n]*\d+\.).*)*/gm;
let matches = input.match(regex).map(s => s.trim());
console.log(matches);

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