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# 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 detect-indent | |
``` | |
## Usage | |
Here we modify a JSON file while persisting the indentation: | |
```js | |
const fs = require('fs'); | |
const detectIndent = require('detect-indent'); | |
/* | |
{ | |
"ilove": "pizza" | |
} | |
*/ | |
const file = fs.readFileSync('foo.json', 'utf8'); | |
// Tries to detect the indentation and falls back to a default if it can't | |
const indent = detectIndent(file).indent || ' '; | |
const 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} - Amount of indentation, for example `2` | |
* `type` {'tab' | 'space' | undefined} - Type of indentation. Possible values are `'tab'`, `'space'` or `undefined` if no indentation is detected | |
* `indent` {string} - Actual indentation | |
## 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: | |
```css | |
html { | |
box-sizing: border-box; | |
} | |
body { | |
background: gray; | |
} | |
p { | |
line-height: 1.3em; | |
margin-top: 1em; | |
text-indent: 2em; | |
} | |
``` | |
[Source.](https://medium.com/@heatherarthur/detecting-code-indentation-eff3ed0fb56b#3918) | |
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: | |
```css | |
body { | |
background: gray; | |
} | |
p { | |
line-height: 1.3em; | |
margin-top: 1em; | |
text-indent: 2em; | |
} | |
``` | |
## Related | |
- [detect-indent-cli](https://github.com/sindresorhus/detect-indent-cli) - CLI for this module | |
- [detect-newline](https://github.com/sindresorhus/detect-newline) - Detect the dominant newline character of a string | |
- [detect-indent-rs](https://github.com/stefanpenner/detect-indent-rs) - Rust port | |
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