locate-character

Get the line and column number of a particular character in a string.

Installation

npm install locate-character, or get it from unpkg.com/locate-character.

Usage

To search for a particular character, using the index or a search string, use locate:

1import { locate } from 'locate-character';
2
3const sample = `
4A flea and a fly in a flue
5Were imprisoned, so what could they do?
6Said the fly, "let us flee!"
7"Let us fly!" said the flea.
8So they flew through a flaw in the flue.
9`.trim();
10
11// Using a character index
12const index = sample.indexOf('fly');
13locate(sample, index);
14// -> { line: 0, column: 13, character: 13 }
15
16// Using the string itself
17locate(sample, 'fly');
18// -> { line: 0, column: 13, character: 13 }
19
20// Using the string with a start index
21locate(sample, 'fly', { startIndex: 14 });
22// -> { line: 2, column: 9, character: 76 }

If you will be searching the same string repeatedly, it's much faster if you use getLocator:

1import { getLocator } from 'locate-character';
2
3const locate = getLocator(sample);
4
5let location = locate(13);
6// -> { line: 0, column: 13, character: 13 }
7
8location = locate('fly', { startIndex: location.character + 1 });
9// -> { line: 2, column: 9, character: 76 }
10
11location = locate('fly', { startIndex: location.character + 1 });
12// -> { line: 3, column: 8, character: 104 }

In some situations (for example, dealing with sourcemaps), you need one-based line numbers:

1getLocator(sample, { offsetLine: 1 });
2locate(sample, { offsetLine: 1 });

There's also an offsetColumn option which is less useful in real-world situations.

License

MIT