How to Parse URLs with JavaScript: the The Easiest Way

Our favorite JavaScript trick is a technique for parsing URLs into parts (host, path, query string etc) that doesn’t require any libraries or advanced regular expressions. It uses only the power of the DOM, and the anchor element <a>.

Let us demonstrate:

JS

$(function(){

 // The URL we want to parse

  var url = 'http://www.ma-no.org/en/content/index_top-12-free-javascript-resources-for-advanced-users-nbsp_1875.php?key=value#comments';

 // The magic: create a new anchor element, and set the URL as its href attribute.

  // Notice that we are accessing the DOM element inside the jQuery object with [0]:

  var a = $('<a>', { href:url } )[0];

 $('#host').val(a.hostname);

  $('#path').val(a.pathname);

  $('#query').val(a.search);

  $('#hash').val(a.hash);

 // Even more:

  // a.port, a.protocol,

  // a.origin (not available in older IE versions)

});

HTML

<ul>

<li><label for="host">Host:</label> <input type="text" id="host" /></li>

<li><label for="path">Path:</label> <input type="text" id="path" /></li>

<li><label for="query">Query String:</label> <input type="text" id="query" /></li>

<li><label for="hash">Hash:</label> <input type="text" id="hash" /></li>

</ul>

CSS

html{

background-color:#f4f4f4;

font:14px/1.4 sans-serif;

color:#666;

}

ul{ list-style:none; width:300px; margin:50px auto; } li{ padding:4px; } input{ font:inherit; border:1px solid #ccc; border-radius:2px; padding:2px 5px; } label{ width:90px; display:inline-block; text-align:right; }

We are using jQuery here but you could use pure JavaScript by creating the anchor element with var a = document.createElement('a'), and then assigning the URL to a.href directly.

Below, another (a bit more) complex example, which lets you type into a textfield and parses the URL in real time:

JS

$(function(){

 // Cache the fields

  var url = $('#url'), host = $('#host'), path = $('#path'), 

  query = $('#query'), hash = $('#hash');

 // Listen for the input event and update the fields

 url.on('input', function(){

  var a = $('<a>', { href:url.val() } )[0];

 host.val(a.hostname);

  path.val(a.pathname);

  query.val(a.search);

  hash.val(a.hash);

  });

 // Set a default URL 

  url.val('http://www.ma-no.org/en/content/index_top-12-free-javascript-resources-for-advanced-users-nbsp_1875.php?key=value#comments');

 // Trigger the input event

  url.trigger('input');

  });

HTML

<div>

<label for="url">Enter a URL:</label> <input type="text" id="url" size="50" />

</div>

<ul id="parts">

  <li><label for="host">Host:</label> <input type="text" id="host" /></li>

  <li><label for="path">Path:</label> <input type="text" id="path" /></li>

  <li><label for="query">Query String:</label> <input type="text" id="query" /></li>

  <li><label for="hash">Hash:</label> <input type="text" id="hash" /></li>

  </ul>

CSS

html{

background-color:#f4f4f4;

font:14px/1.4 sans-serif;

color:#666;

}

ul{

  list-style:none;

  width:300px;

  margin:0 auto;

  }

li{

  padding:4px;

  }

input{

  font:inherit;

  border:1px solid #ccc;

  border-radius:2px;

  padding:2px 5px;

  }

label{

  width:90px;

  display:inline-block;

  text-align:right;

  }

div{

  padding:40px;

  text-align:center;

  }

The difference here is that we are listening for the input event (not supported in older IEs) which notifies the event listener on every change of the field’s value.

One useful application of this technique is to treat external links differently.

For example, you can add an icon next to each link that points offsite, or you can display some sort of intermediate page that alerts people that they are being redirected to a third party website.

To detect external links, we will compare the hostname properties of the DOM element and the location object:

JS

$(function(){

 // Get only the external links:

  var external = $('a[href]').filter(function(){

  return this.hostname != location.hostname;

  });

 // In the return above, you may also compare the protocol 

  // property if you wish to distinguish http from https links.

 external.addClass('external');

});

HTML

<a href="?page=123">Page 1</a>

  <a href="/page2.html">Page 2</a>

  <a href="http://demo.ma-no.org/">Page 3</a>

  <a href="http://ma-no.org/page3.html">Page 4</a>

<a href="http://google.com/">Page 5</a>

CSS

html{

background-color:#f4f4f4;

font:15px/1.4 sans-serif;

color:#666;

}

body{

  padding:50px;

  text-align:center;

  }

a{

  color:#999;

  }

a.external{

  color:green;

  }

a.external:after{

  content:'put your icon ';

  }

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN END DEVELOPMENT.