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Node module to convert efficiently index to/from line-column in a string.
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README.md

line-column

wercker status Coverage Status npm version

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.
    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

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 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/ 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)

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