Skip to main content

Getting notifications of Network Status changes using online and offline events introduced in HTML5

I was working on an online\offline application, wherein I wanted to display a set of records stored in the local database to the user when he goes offline. The only way to determine the network status is to send a XHR request to the server at particular time intervals (polling). If the server responds back with some data it is understood that the user is online. However, I came across two event listeners 'ononline' and 'onoffline' which are triggered when the network status changes. Sample Code: These event listeners are not supported in every browser, I have tested this on Chrome 11 and it works great. Here is the code snippet that I have used in my application:
function showOnlineStatus() {     var status = document.getElementById('userStatus');     if(navigator.onLine)         status.innerHTML = status.className = 'online';     else         status.innerHTML = status.className = 'offline'; } window.onload = window.ononline = window.onoffline = showOnlineStatus;

As seen in the above code, the navigator object has an attribute onLine which is used to determine network status. It is set to true if the user is online and false otherwise. To test this, unplug the network cable and see that the offline event gets triggered. On connecting the network cable the online event would be triggered.
Labels:

Comments

  1. Cyril HanquezJune 9, 2011 at 12:19 AM

    Hi Sagar,

    sadly it's badly and differently supported by the browsers so I would not rely on it. Also if your router lose the internet connection, it won't be detected as the computer is still connected to the router.

    ReplyDelete
  2. RaymondJune 9, 2011 at 12:33 AM

    I think the point though is that it could be helpful. You could warn a user about them being offline - or use local storage to temporarily store stuff until they get back online.

    ReplyDelete
  3. Sagar GanatraJune 9, 2011 at 9:51 AM

    @Cyril,

    You're correct. This is not supported across the browsers (I have mentioned this in my post). However, once other browsers implement this feature we would not be facing this problem.

    ReplyDelete
  4. Esay leozMay 20, 2013 at 1:19 PM

    HDMI v1.4 Cable connection - High Velocity together with Ethernet


    It may find puzzling while using hundreds of cables in the marketplace along with every one of the mis-information in relation to version 1. 3 & 1. 4, ethernet along with length limitations. Exactly why certainly not preserve every one of the anxiety & merely purchase a cable tv of which functions?

    Zero publicity. Zero N. Utes. No worries! - Most of these cables are made to the highest expectations along with constructed with challenging PVC coat along with deterioration . proof Precious metal Fittings to give it the top effectiveness. Potential evidence along with fully backwards works with most HDMI expectations. Meaning; An individual don't have to purchase further cables if you haven't however upgraded your entire system - Most of these cables WORKS!

    ReplyDelete

Post a Comment

Popular posts from this blog

Custom validation messages for HTML5 Input elements using the constraint validation API

HTML5 has introduced several input types such as EMAIL, URL, RANGE, SEARCH, DATE, TIME, etc,. Most of the modern browsers have implemented them and are ready to be used in a HTML document. Another exciting feature introduced in HTML5 is the form validation. Instead of writing JavaScript to validate users input, browsers can now validate it and show an appropriate message if the validation fails. The validation message is shown in line with the field for which the validation has failed. The default error message is shown when the validation fails. In this post I'll explain how these error messages can be changed.
54 comments
Read more

De-obfuscating javascript code in Chrome Developer Tools

I had blogged about JavaScript debugging with Chrome Developer Tools some time back, wherein I have explained how these developer tools can help in debugging javascript code. Today Google Chrome 12 was released and my Chrome browser was updated to this version. As with every release, there have been some improvements made on performance, usability etc,. One feature that stood out for me is the ability to De-obfuscate the javascript code.

What is Minification?

Minification is the process of removing unnecessary characters such as white spaces, comments, new lines from the source code. These otherwise would be added to make the code more readable. Minifying the source code helps in reducing the file size and thereby reducing the time taken to download the file. This is the reason why most of the popular javascript libraries such as jQuery are minified. A minified jQuery file is of 31 KB in size where as an uncompressed one is about 229 KB. Unfortunately, debugging minified javascript file…
37 comments
Read more

Adding beforeRender and afterRender functions to a Backbone View

I was working on a Backbone application that updated the DOM when a response was received from the server. In a Backbone View, the initialize method would perform some operations and then call the render method to update the view. This worked fine, however there was scenario where in I wanted to perform some tasks before and after rendering the view. This can be considered as firing an event before and after the function had completed its execution. I found a very simple way to do this with Underscore's wrap method.
29 comments
Read more