Tag Archives: Software Development

Event Namespacing: It’s A Good Idea

If you’re a web developer and use jQuery chances are you have had, or will have, the need to attach event handlers to your page elements.

With jQuery you can do this in a number of ways .on, .bind, directly with .click (blur, mouseout, etc…), and more.  For more information regarding adding handlers and removing them see the jQuery API documentation.

A quick example using .bind:

$( "selector" ).bind( "click", function() {
//do something;

And if you ever needed to remove your handler you could do something like:
$( "selector" ).unbind( "click");

This is all very simple and works great.  However, what if you need to remove a specified handler?  For example, if you’re writing a plugin and need to remove only the plugin’s custom handlers.

Both jQuery functions .off and .unbind allow you to pass in the method signature to remove the specified handler. However, this requires you to maintain a reference to the handler which may not be ideal.

This is where event namespacing can come in handy.  Adding a namesspace to your handler when you attach it allows you to safely remove it later without removing all event handlers of the same type.

Here are the same bind and unbind methods using a namespace:

$( "selector" ).bind( "click.mynamespace", function() {
//do something;

$( "selector" ).unbind( "click.mynamespace");

Namespaces gives you the flexibility to unbind specific event handlers while maintaining the ability to unbind by event type or all handlers at once.  It can also be used in the same way to trigger a specific event handler.  And it’s a good practice to easily identify custom event handlers, especially when developing plugins.


Floating Sidebar With CSS

Floating sidebars are a great method for keeping menus, share buttons, and other information in front of users as they scroll down the page. There are a number of jQuery plugins that work great for this, but in some cases jQuery might be overkill. For example, if you need to keep informational or help text that is static in front of the user.

A simple way to create a floating sidebar is to use CSS. Take a look at the side bar on the left and scroll down the page this jsfiddle test. Notice, it stays in view the entire time. To achieve this all we have to do is create a div with the following class.

position: fixed;
z-index: 1000;

The magic is “position: fixed”, it’s what makes the sidebar stay where you want it to. Depending on what else you have on the page, and perhaps if you want it to float outside the container the div is in, I like to use z-index to make sure it overlaps how I want it to.

Now that you have it floating you need to position the div and style it by adding another class like below. In this case the div will float on the left and start below the header of the page.

width: 300px;
padding: 0px 0px 0px 0px;

There you have it, in just a few minutes you have a quick and easy solution for creating a floating sidebar.

Visual Studio Switches

Visual Studio offers a number of command line switches that allow you to run the IDE and perform a specified task.  You can get a complete list and more information here Visual Studio Command Line Switches .

Here are a couple I’ve used.

First /ResetSkipPkgs:

This comes in handy when updating a web reference and get this error: “The components required to enumerate web references are not installed on this computer…”  The error goes on to suggest re-installing visual studio.  But, what this really means is at some point during start up a visual studio extension did threw and error and you said yes to not load it in the future.  All you need to do is run the above command and you should be able to update your web reference.

Second /Log:

Running this will create …\Application Data\Microsoft\VisualStudio\9.0\ActivityLog.xml.  I haven’t used this personally, but the vendor of a third party tool I’m using asked for it to help troubleshoot an issue.  I thought I’d pass it along.

Unit Testing JavaScript with MSTest and JSTest.Net

JavaScript: A necessary evil

I’ve always found that while JavaScript was a powerful tool for web development it could be a real pain to test and debug.  Until now I pushed through the pain with good old fashioned manual testing and the debugging tools available in web browsers.  Recently, I was developing a web page that needed a lot of client side calculations and data manipulation. I decided it was time to man up and find a way to unit test client side JavaScript.

I Wanted

  1. Integration with MSTest
  2. Writing unit tests with server-side code as I do for C# code
  3. Running JavaScript and C# unit tests together in harmony
  4. Nothing to install so others can just start using the testing library
  5. No web browser required

Surprise and Delight
A few minutes on Google and I found a solution that appeared to be the answer. Before I go on, I should mention I found several testing libraries so there are many options. Most of which integrate with MSTest and most other testing frameworks.

The winner is
I selected to use JSTest.Net

It was pretty simple to get up and running:

  1. Just download the dll from JSTest.Net
  2. Made a reference to it in my test project
  3. Added a couple using statements in my test class
  4. Started writing tests

Consider this JavaScript example

function calculateMarketPrice(value, quantity, factor) {
    return (value / quantity) * factor;

It’s pretty simple, send in a few parameters and return a value.  However, testing this manually and debugging through the web browser is not always as simple, especially if it’s implemented on complex web pages.  In a lot of cases it’s tedious and inefficient.  Even worse it could be ineffective and bugs could be missed.  For example, maybe there’s a rounding issue?  Or maybe a null parameter won’t be handled as expected.  We just don’t know unless we test for it.  And when testing is difficult it’s more likely to be missed or god forbid skipped.

Test Class Example

using Microsoft.VisualStudio.TestTools.UnitTesting;
using JSTest;
using JSTest.ScriptLibraries;

namespace JavaScriptTestProject
    public class CommonJavaScriptTests
        private readonly TestScript _commonTestScript = new TestScript();

        public CommonJavaScriptTests()
            _commonTestScript.AppendBlock(new JsAssertLibrary());
        public TestContext TestContext { get; set; }

        public void GivenValueQuantityAndFactorTheCorrectMarketPriceIsReturned()
            _commonTestScript.RunTest(@"assert.equal(99.26, calculateMarketPrice(49630, 50000, 100));", true);

A quick overview
The library uses a class called TestScipt as a wrapper  to command line scripts (CScript). Before writing tests it’s necessary to add the script file you’ll be testing and any additional libraries to the TestScript.   In my example I used the AppendFile method to add my js file and the AppendBlock to add the assertion library included with JSTest.   According to the documentation there are other assertion libraries and mocking libraries available but I have not tried them yet.

Once the scripts are appended to the TestScript class the RunTest method can be invoked.  It takes the script block to be tested as the first parameter and has an overload that includes a boolean to turn debug off and on.  When debug is on and you select to debug your test it allows you to step into the debug test script and from there into your script. This is awesome. Not only do I get to easily test every scenario I can think of, I get to debug it too!

JsTest Documentation

Other Things

  • My example uses MSTest but it works with other test frameworks
  • The documentation says it only works with VS2010, But I have it working in 2008

With testing libraries that are compatible with most frameworks available there are no excuses for not covering JavaScript with unit tests. And the integration with the visual studio just in time debugger is icing on the cake. It’s also worth noting I’ve since used this library for more complicated tests that included date manipulation and JSON and found it just as effective.

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