Node.js get file extension

import extname in order to return the extension the file:
```
import { extname } from 'path';
extname(file.originalname);
```

where file is the file 'name' of form

You can use [path.parse(path)][1], for example

```JavaScript
const path = require('path');
const { ext } = path.parse('/home/user/dir/file.txt');
```

[1]:

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Try this one

```js
const path = require('path');

function getExt(str) {
const basename = path.basename(str);
const firstDot = basename.indexOf('.');
const lastDot = basename.lastIndexOf('.');
const extname = path.extname(basename).replace(/(\.[a-z0-9]+).*/i, '$1');

if (firstDot === lastDot) {
return extname;
}

return basename.slice(firstDot, lastDot) + extname;
}

// all are `.gz`
console.log(getExt('/home/charlike/bar/file.gz'));
console.log(getExt('/home/charlike/bar/file.gz~'));
console.log(getExt('/home/charlike/bar/file.gz+cdf2'));
console.log(getExt('/home/charlike/bar/file.gz?quz=zaz'));

// all are `.tar.gz`
console.log(getExt('/home/charlike/bar/file.tar.gz'));
console.log(getExt('/home/charlike/bar/file.tar.gz~'));
console.log(getExt('/home/charlike/bar/file.tar.gz+cdf2'));
console.log(getExt('/home/charlike/bar/file.tar.gz?quz=zaz'));

```

A one liner which extends `String.prototype`:

```
Object.defineProperty(String.prototype, "ext", {get: function(x) {return this.split('.').pop()}})
str = 'fox.fbx';
str.ext
```

Result:

[![enter image description here][1]][1]


[1]:

I believe you can do the following to get the extension of a file name.

```javascript
var path = require('path')

path.extname('index.html')
// returns
'.html'
```

If you would like to get all extensions in a file name (e.g. `filename.css.gz` => `css.gz`), try this:

```javascript
const ext = 'filename.css.gz'
.split('.')
.filter(Boolean) // removes empty extensions (e.g. `filename...txt`)
.slice(1)
.join('.')

console.log(ext) // prints 'css.gz'
```

```js
const path = require('path');

function getExt(str) {
const basename = path
.basename(str)
// Patch: for hidden files
// Removes all dots at the beginning of a line
.replace(/^(\.+)/i, '');

const firstDot = basename.indexOf('.');
const lastDot = basename.lastIndexOf('.');
const extname = path.extname(basename).replace(/(\.[a-z0-9]+).*/i, '$1');

if (firstDot === lastDot) {
return extname;
}

return basename.slice(firstDot, lastDot) + extname;
}
```
```js
const files = [
'/home/charlike/bar/.hidden.tar.gz~', // ".tar.gz"
'/home/charlike/bar/file.tar.gz~', // ".tar.gz"
'/home/charlike/bar/file.tar.gz+cdf2', // ".tar.gz"
'/home/charlike/bar/file.tar.gz?quz=zaz', // ".tar.gz"
];

const fileAndExt = files.map((file) => [ file, getExt(file) ]);

console.log(JSON.stringify(fileAndExt, null, 2));
```

Using `path` is not really reliable as it depends on extension name being in the file name, which is not always the case.

You should use [file-type package][1] it detects extension by checking the magic number of the buffer, rather than depending on name of the file which not always have extension in it.


[1]:

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