# line-column
[](https://travis-ci.org/io-monad/line-column) [](https://coveralls.io/github/io-monad/line-column?branch=master) [](https://badge.fury.io/js/line-column)
Node module to convert efficiently index to/from line-column in a string.
## Install
npm install line-column
## Usage
### lineColumn(str, options = {})
Returns a `LineColumnFinder` instance for given string `str`.
#### Options
| Key | Description | Default |
| ------- | ----------- | ------- |
| `origin` | The origin value of line number and column number | `1` |
### lineColumn(str, index)
This is just a shorthand for `lineColumn(str).fromIndex(index)`.
### LineColumnFinder#fromIndex(index)
Find line and column from index in the string.
Parameters:
- `index` - `number` Index in the string. (0-origin)
Returns:
- `{ line: x, col: y }` Found line number and column number.
- `null` if the given index is out of range.
### LineColumnFinder#toIndex(line, column)
Find index from line and column in the string.
Parameters:
- `line` - `number` Line number in the string.
- `column` - `number` Column number in the string.
or
- `{ line: x, col: y }` - `Object` line and column numbers in the string.<br>A key name `column` can be used instead of `col`.
or
- `[ line, col ]` - `Array` line and column numbers in the string.
Returns:
- `number` Found index in the string.
- `-1` if the given line or column is out of range.
## Example
```js
var lineColumn = require("line-column");
var testString = [
"ABCDEFG\n", // line:0, index:0
"HIJKLMNOPQRSTU\n", // line:1, index:8
"VWXYZ\n", // line:2, index:23
"日本語の文字\n", // line:3, index:29
"English words" // line:4, index:36
].join(""); // length:49
lineColumn(testString).fromIndex(3) // { line: 1, col: 4 }
lineColumn(testString).fromIndex(33) // { line: 4, col: 5 }
lineColumn(testString).toIndex(1, 4) // 3
lineColumn(testString).toIndex(4, 5) // 33
// Shorthand of .fromIndex (compatible with find-line-column)
lineColumn(testString, 33) // { line:4, col: 5 }
// Object or Array is also acceptable
lineColumn(testString).toIndex({ line: 4, col: 5 }) // 33
lineColumn(testString).toIndex({ line: 4, column: 5 }) // 33
lineColumn(testString).toIndex([4, 5]) // 33
// You can cache it for the same string. It is so efficient. (See benchmark)
var finder = lineColumn(testString);
finder.fromIndex(33) // { line: 4, column: 5 }
finder.toIndex(4, 5) // 33
// For 0-origin line and column numbers
var oneOrigin = lineColumn(testString, { origin: 0 });
oneOrigin.fromIndex(33) // { line: 3, column: 4 }
oneOrigin.toIndex(3, 4) // 33
```
## Testing
npm test
## Benchmark
The popular package [find-line-column](https://www.npmjs.com/package/find-line-column) provides the same "index to line-column" feature.
Here is some benchmarking on `line-column` vs `find-line-column`. You can run this benchmark by `npm run benchmark`. See [benchmark/](benchmark/) for the source code.
```
long text + line-column (not cached) x 72,989 ops/sec ±0.83% (89 runs sampled)
long text + line-column (cached) x 13,074,242 ops/sec ±0.32% (89 runs sampled)
long text + find-line-column x 33,887 ops/sec ±0.54% (84 runs sampled)
short text + line-column (not cached) x 1,636,766 ops/sec ±0.77% (82 runs sampled)
short text + line-column (cached) x 21,699,686 ops/sec ±1.04% (82 runs sampled)
short text + find-line-column x 382,145 ops/sec ±1.04% (85 runs sampled)
```
As you might have noticed, even not cached version of `line-column` is 2x - 4x faster than `find-line-column`, and cached version of `line-column` is remarkable 50x - 380x faster.
## Contributing
1. Fork it!
2. Create your feature branch: `git checkout -b my-new-feature`
3. Commit your changes: `git commit -am 'Add some feature'`
4. Push to the branch: `git push origin my-new-feature`
5. Submit a pull request :D
## License
MIT (See LICENSE)
