# 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
import fs from 'node:fs';
import detectIndent from '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, undefined, 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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