Using Javascript’s Location Object to Work with URLs

JavaScript gives you many ways to access and change the current URL that is displayed in the visitor’s browser. All these techniques use the Location object, which is itself a property of the Window object. You can create a new Location object that contains the current URL as follows:

var currentURL = window.location;

In this tutorial, you explore all the properties and methods of the Location object. You learn:

• How to read all the different parts of a URL
• How to send the visitor to another page by changing the URL, and
• How to automatically reload or refresh the page.

The anatomy of a URL

A URL can be broken down into as many as six components, though many of them are optional:

<protocol>//<hostname>:<port>/<pathname><search><hash>

Here’s an example of a URL with all these components:

http://www.example.com:80/example.cgi?x=3&y=4#results

In this example, http: is the protocol, www.example.com is the hostname, 80 is the port, /example.cgi is the pathname, ?x=3&y=4 is the search, or query string, and #results is the hash, or the anchor to display within the page.

Reading the current URL through the Location object

You can access all of these URL components using Location properties of the same names. You can also access the following properties:

host

Contains the hostname and the port combined into one string, e.g. www.example.com:80

href

Contains the complete URL, e.g. http://www.example.com:80/example.cgi?x=3&y=4#results

Here are some examples (assume that the example URL above is displayed in the browser’s address bar at the time the code below is run):

var currentURL = window.location;
alert ( currentURL.href );     // Displays 'http://www.example.com:80/example.cgi?x=3&y=4#results'
alert ( currentURL.protocol ); // Displays 'http:'
alert ( currentURL.host );     // Displays 'www.example.com:80'
alert ( currentURL.hostname ); // Displays 'www.example.com'
alert ( currentURL.port );     // Displays '80'
alert ( currentURL.pathname ); // Displays '/example.cgi'
alert ( currentURL.search );   // Displays '?x=3&y=4'
alert ( currentURL.hash );     // Displays '#results'

Manipulating the URL using the Location object

You can use the href property of the Location object to send visitors to a completely different page:

window.location.href = "http://www.example.com/anotherpage.html";

Here’s a simple example:

<input type="button" onclick="window.location.href='http://www.google.com/'" value="Visit www.google.com" />

Here’s the resulting button. Click it to visit www.google.com if you like, then close the window to return here.

Setting the Location.href property like this keeps the previous URL in the browser’s history, so the visitor can click the Back button to return to the previous page. If you don’t want the visitor to be able to go back to the previous URL, use Location.replace() instead:

window.location.replace ( "http://www.example.com/anotherpage.html" );

This loads the new URL, and also replaces the current history entry with the new URL, so that the previous URL is effectively wiped from the history.

As well as redirecting the browser to a different URL, you can selectively change parts of the current URL using the Location object properties. For example, to change the URL’s hash to a different anchor within the page:

window.location.hash = "#moreResults";

Here’s an example:

<input type="button" onclick="window.location.hash='#top'" value="Jump to the top of the page" />

…and here’s the resulting button (scroll to the bottom of the page to see it). Click it, and your browser moves to the top of the page. That’s because the page contains an anchor named #top at the top. Notice how the URL changes in the browser’s address bar. (You can close the window afterwards to return here.)

Reloading the page

Finally, you can use the Location.reload() method to force the browser to reload the current URL, just as if the visitor had clicked their Reload/Refresh button:

window.location.reload ( );

To force the browser to retrieve the page directly from the server, bypassing any caches, pass a true parameter to Location.reload():

window.location.reload ( true );

Here’s an example that uses Location.reload() to create a button to refresh the page:

<input type="button" onclick="window.location.reload()" value="Reload the page" />

Here’s the button — click it to see it in action!

Summary

You’ve now explored all the properties and methods of JavaScript’s Location object. This object is useful for:

• Reading the current URL — for example, to see what query parameters have been included in the URL. Good if you’re creating dynamic JavaScript pages.
• Changing the current URL — so you can move to a different point in the page, or send visitors off to a different page. This allows you to do things like JavaScript drop-down menus for navigation.
• Reloading the current page — either in response to a button click, or automatically. For example, you can use Location.reload() with setTimeout() or setInterval() to reload the page periodically.