# relateurl [![NPM Version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Dependency Status][david-image]][david-url]

> Minify URLs by converting them from absolute to relative.

If you were to use this library on a website like `http://example.com/dir1/dir1-1/`, you would get results such as:

| Before                                      | After                                |
| :------------------------------------------ | :----------------------------------- |
| `http://example.com/dir1/dir1-2/index.html` | `../dir1-2/`                         |
| `http://example.com/dir2/dir2-1/`           | `/dir2/dir2-1/`                      |
| `http://example.com/dir1/dir1-1/`           | ` `                                  |
| `https://example.com/dir1/dir1-1/`          | `https://example.com/dir1/dir1-1/`   |
| `http://google.com:80/dir/`                 | `//google.com/dir/`                  |
| `../../../../../../../../#anchor`           | `/#anchor`                           |

**All string parsing.** *No* directory browsing. It is thoroughly tested, very fast and lightweight with zero external dependencies.

## Getting Started

This utility requires [Node.js](http://nodejs.org/) `>= 0.10`. To install, type this at the command line:
```
npm install relateurl --save-dev
```

### Options

#### options.defaultPorts
Type: `Object`   
Default value: `{ftp:21, http:80, https:443}`  

Extend the list with any ports you need. Any URLs containing these default ports will have them removed. Example: `http://example.com:80/` will become `http://example.com/`.

#### options.directoryIndexes
Type: `Array`   
Default value: `["index.html"]`  

Extend the list with any resources you need. Works with [`options.removeDirectoryIndexes`](#options.removeDirectoryIndexes).

#### options.ignore_www
Type: `Boolean`  
Default value: `false`  

This will, for example, consider any domains containing `http://www.example.com/` to be related to any that contain `http://example.com/`.

#### options.output
Type: constant or `String`  
Choices: `RelateUrl.ABSOLUTE`,`RelateUrl.PATH_RELATIVE`,`RelateUrl.ROOT_RELATIVE`,`RelateUrl.SHORTEST`  
Choices: `"absolute"`,`"pathRelative"`,`"rootRelative"`,`"shortest"`  
Default value: `RelateUrl.SHORTEST`  

`RelateUrl.ABSOLUTE` will produce an absolute URL. Overrides [`options.schemeRelative`](#options.schemeRelative) with a value of `false`.  
`RelateUrl.PATH_RELATIVE` will produce something like `../child-of-parent/etc/`.  
`RelateUrl.ROOT_RELATIVE` will produce something like `/child-of-root/etc/`.  
`RelateUrl.SHORTEST` will choose whichever is shortest between root- and path-relative.  

#### options.rejectedSchemes
Type: `Array`   
Default value: `["data","javascript","mailto"]`  

Extend the list with any additional schemes. Example: `javascript:something` will not be modified.

#### options.removeAuth
Type: `Boolean`   
Default value: `false`  

Remove user authentication information from the output URL.

#### options.removeDirectoryIndexes
Type: `Boolean`   
Default value: `true`  

Remove any resources that match any found in [`options.directoryIndexes`](#options.directoryIndexes).

#### options.removeEmptyQueries
Type: `Boolean`   
Default value: `false`  

Remove empty query variables. Example: `http://domain.com/?var1&var2=&var3=asdf` will become `http://domain.com/?var3=adsf`. This does not apply to unrelated URLs (with other protocols, auths, hosts and/or ports).

#### options.removeRootTrailingSlash
Type: `Boolean`   
Default value: `true`  

Remove trailing slashes from root paths. Example: `http://domain.com/?var` will become `http://domain.com?var` while `http://domain.com/dir/?var` will not be modified.

#### options.schemeRelative
Type: `Boolean`   
Default value: `true`  

Output URLs relative to the scheme. Example: `http://example.com/` will become `//example.com/`.

#### options.site
Type: `String`   
Default value: `undefined`  

An options-based version of the [`from`](#examples) argument. If both are specified, `from` takes priority.

#### options.slashesDenoteHost
Type: `Boolean`   
Default value: `true`  

Passed to Node's [`url.parse`](http://nodejs.org/api/url.html#url_url_parse_urlstr_parsequerystring_slashesdenotehost).

### Examples
This library can be used as a [function for single-use](#single-instance) or as a [class for multiple conversions](#reusable-instances).

Upon successful conversion, a `String` will be returned. If an issue is encountered while parsing `from`, an error will be thrown.

#### Single Instance
```js
var RelateUrl = require("relateurl");

var result = RelateUrl.relate(from, to, options);
```

#### Reusable Instances
```js
var RelateUrl = require("relateurl");

var instance = new RelateUrl(from, options);

var result1 = instance.relate(to1);
var result2 = instance.relate(to2, customOptions);
var result3 = instance.relate(to3);
```

## FAQ
1. **Why bother writing/using this?**  
To aid in further minifying HTML, mainly for the purpose of faster page loads and SEO. It's been integrated into [HTMLMinifier](https://github.com/kangax/html-minifier).

2. **Why not just use Node's `url.parse`, `url.resolve` and `path.relative`?**  
`url.parse` *is* used, but `url.resolve` and `path.relative` are both slower and less powerful than this library.


## Release History
* 0.2.7 Node v6 support
* 0.2.6 minor enhancements
* 0.2.5 added `options.removeRootTrailingSlash`
* 0.2.4 added `options.site`
* 0.2.3 added browserify npm-script
* 0.2.2 removed task runner
* 0.2.1 shorten resource- and query-relative URLs, test variations list with other site URLs
* 0.2.0 code cleanup, `options.removeEmptyQueries=true` only applied to unrelated URLs
* 0.1.0 initial release


## Roadmap
* 0.2.8 check if queries are the same, regardless of param order
* 0.2.8 possible [scheme exclusions](http://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml) such as `tel:`
* 0.2.8 decipher and return invalid input (special cases) to complete test suite
* 0.3.0 test `options.slashesDenoteHost=false`, add something like `options.externalDirectoryIndexes=[]` for external sites


[npm-image]: https://img.shields.io/npm/v/relateurl.svg
[npm-url]: https://npmjs.org/package/relateurl
[travis-image]: https://img.shields.io/travis/stevenvachon/relateurl.svg
[travis-url]: https://travis-ci.org/stevenvachon/relateurl
[david-image]: https://img.shields.io/david/stevenvachon/relateurl.svg
[david-url]: https://david-dm.org/stevenvachon/relateurl