detect-indent

Detect the indentation of code

Pass in a string of any kind of text and get the indentation.

Use cases

• Persisting the indentation when modifying a file.
• Have new content match the existing indentation.
• Setting the right indentation in your editor.

Install

$ npm install --save detect-indent

Usage

// modify a JSON file while persisting the indentation in Node
var fs = require('fs');
var detectIndent = require('detect-indent');
/*
{
    "ilove": "pizza"
}
*/
var file = fs.readFileSync('foo.json', 'utf8');
// tries to detect the indentation and falls back to a default if it can't
var indent = detectIndent(file).indent || '    ';
var json = JSON.parse(file);

json.ilove = 'unicorns';

fs.writeFileSync('foo.json', JSON.stringify(json, null, indent));
/*
{
    "ilove": "unicorns"
}
*/

API

Accepts a string and returns an object with stats about the indentation:

• amount: {Number} the amount of indentation, e.g. 2
• type: {String|Null} the type of indentation. Possible values are tab, space or null if no indentation is detected
• indent: {String} the actual indentation

CLI

$ npm install --global detect-indent

$ detect-indent --help

  Usage
    detect-indent <file>
    echo <string> | detect-indent

  Example
    echo '  foo\n  bar' | detect-indent | wc --chars
    2

Algorithm

The current algorithm looks for the most common difference between two consecutive non-empty lines.

In the following example, even if the 4-space indentation is used 3 times whereas the 2-space one is used 2 times, it is detected as less used because there were only 2 differences with this value instead of 4 for the 2-space indentation:

html {
  box-sizing: border-box;
}

body {
  background: grey;
}

p {
    line-height: 1.3em;
    margin-top: 1em;
    text-indent: 2em;
}

Source.

Furthermore, if there are more than one most used difference, the indentation with the most lines is selected.

In the following example, the indentation is detected as 4-spaces:

body {
  background: grey;
}

p {
    line-height: 1.3em;
    margin-top: 1em;
    text-indent: 2em;
}

License

MIT © Sindre Sorhus