113 lines
2.5 KiB
Markdown
113 lines
2.5 KiB
Markdown
# detect-indent [](https://travis-ci.org/sindresorhus/detect-indent)
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> Detect the indentation of code
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Pass in a string of any kind of text and get the indentation.
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## Use cases
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- Persisting the indentation when modifying a file.
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- Have new content match the existing indentation.
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- Setting the right indentation in your editor.
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## Install
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```
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$ npm install detect-indent
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```
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## Usage
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Here we modify a JSON file while persisting the indentation:
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```js
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const fs = require('fs');
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const detectIndent = require('detect-indent');
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/*
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{
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"ilove": "pizza"
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}
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*/
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const file = fs.readFileSync('foo.json', 'utf8');
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// Tries to detect the indentation and falls back to a default if it can't
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const indent = detectIndent(file).indent || ' ';
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const json = JSON.parse(file);
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json.ilove = 'unicorns';
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fs.writeFileSync('foo.json', JSON.stringify(json, null, indent));
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/*
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{
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"ilove": "unicorns"
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}
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*/
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```
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## API
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Accepts a string and returns an object with stats about the indentation:
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* `amount` {number} - Amount of indentation, for example `2`
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* `type` {'tab' | 'space' | undefined} - Type of indentation. Possible values are `'tab'`, `'space'` or `undefined` if no indentation is detected
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* `indent` {string} - Actual indentation
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## Algorithm
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The current algorithm looks for the most common difference between two consecutive non-empty lines.
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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:
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```css
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html {
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box-sizing: border-box;
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}
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body {
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background: gray;
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}
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p {
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line-height: 1.3em;
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margin-top: 1em;
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text-indent: 2em;
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}
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```
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[Source.](https://medium.com/@heatherarthur/detecting-code-indentation-eff3ed0fb56b#3918)
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Furthermore, if there are more than one most used difference, the indentation with the most lines is selected.
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In the following example, the indentation is detected as 4-spaces:
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```css
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body {
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background: gray;
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}
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p {
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line-height: 1.3em;
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margin-top: 1em;
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text-indent: 2em;
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}
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```
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## Related
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- [detect-indent-cli](https://github.com/sindresorhus/detect-indent-cli) - CLI for this module
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- [detect-newline](https://github.com/sindresorhus/detect-newline) - Detect the dominant newline character of a string
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- [detect-indent-rs](https://github.com/stefanpenner/detect-indent-rs) - Rust port
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## License
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MIT © [Sindre Sorhus](https://sindresorhus.com)
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