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This bookmarklet display the timing information that is available using the W3C NavigationTiming API. I found this is a simpler way at seeing what the performance of a page is verse opening up the developer tools every time. This bookmarklet can be used in:

  • Latest Chrome Build
  • Firefox 7+
  • IE 9+ (Still need to test)

On mobile devices is can be used on:

  • Windows Phone 7.5 (Mango)
  • Andriod Ice cream sandwich

Using It

I have written a blog about this and you can find the bookmarket instructions there. Why? I tried to get the code for the bookmarklet in the markdown but it strips the javascript. This makes sense

Blog article on the Bookmarklet

Development Approach

I took a different a to building the bookmarklet. The only components to the booklet are jquery, ViewJS the new jquery templates and github. Before starting, I looked at a lot of bookmarklet but they all kind of sucked at their approach:

1.) Need to hand build the DOM 2.) Hosting the bookmarklet was a pain 3.) The way the javascript was compiled into a single file was not easy to maintain

So how does this bookmarklet's architecture resolve this problems?

Bookmarklet link

The bookmarklet link is very simple and calls out to an

    var w3cnavjs=document.createElement('SCRIPT');

The code for the bookmarklet does only two things:

1.) Captures the W3C NavigationTiming Data 2.) Encodes it into a JSON String 3.) Creates an iframe and passes the data to the iframe in the hash

//Add the data as the hash. The iframe will pull the data.
$('#w3c-nav-iframe').attr('src', ""+JSON.stringify(data));

Why use an iframe?

I tried several ways to do this. Ideally I would not need to use an iframe but because the template was loaded from a file on the server. I needed to domain, which caused a cross domain issue. Yes, I could have encoded the HTML into a string and had it embedded in the JavaScript but this would have increased the maintenance cost of the bookmarklet. If i wanted to change any UI or add a new feature changing the minified HTML string would have been worse than building the DOM structure by JavaScript alone.

My iframe

The source of my iframe is "w3c-nav-bookmarklet.html" file which when loaded will run the following code:

    //Need to pull off the "#" from the string
    var data = window.location.hash.substring(1);
    //if the string is empty that means there is no data and the browser does
    //not support the API.
    if (data != ""){
        data = JSON.parse(data);

The final phase of the bookmarklet is handed over to $.render(); and the bookmarklet UI is displayed using a template. This greatly simplifies the development of the UI, and means i can concentrate on the features. Why is this simpler? Because it allows me to just use HTML in its natural form and let the $.render(); function insert the data UI where it needs to go.

<div class="section">
    <div class="leftBox height1">
    <div class="rightBox">
        <div class="timingName">
            Redirect Start
        <div class="timingData">
            <!-- This will be replaced with the data --> 

Why use github to host?

Even though i am the CTO of, deploying stuff into production easily required working with our operations team or setting up a separate server environment. The bookmarklet requires no server side other than serving files so, i figured using the Github pages would simplify everything.

Now when i want to release a new version i can just push the code into my gh-pages branch and the new version will automatically be deployed. No need for a separate deployment script for the website.

Setting up github pages

This was fairly straightforward; i just followed the instructions here. My branching strategy for the project is different from my other repositories. In this project, i use the "gh-pages" branch as the master/production branch and use the "master" branch as my development branch.


Make the bookmarklet scroll to the top of the page. Make the bookmarklet go aways smoothly. Now it leaves the iframe behind.

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