locate-character

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:

import { locate } from 'locate-character';

const sample = `
A flea and a fly in a flue
Were imprisoned, so what could they do?
Said the fly, "let us flee!"
"Let us fly!" said the flea.
So they flew through a flaw in the flue.
`.trim();

// Using a character index
const index = sample.indexOf('fly');
locate(sample, index);
// -> { line: 0, column: 13, character: 13 }

// Using the string itself
locate(sample, 'fly');
// -> { line: 0, column: 13, character: 13 }

// Using the string with a start index
locate(sample, 'fly', { startIndex: 14 });
// -> { line: 2, column: 9, character: 76 }

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

import { getLocator } from 'locate-character';

const locate = getLocator(sample);

let location = locate(13);
// -> { line: 0, column: 13, character: 13 }

location = locate('fly', { startIndex: location.character + 1 });
// -> { line: 2, column: 9, character: 76 }

location = locate('fly', { startIndex: location.character + 1 });
// -> { line: 3, column: 8, character: 104 }

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

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

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

License

MIT