Brian Dukes, Web Developer

DNN World 2012

bdukes — Mon, 15 Oct 2012 18:35:00 GMT

I just returned from DotNetNuke 2012 and wrote up a review of the experience at my Engage Software blog ....(read more)

Day of DotNetNuke Recap

bdukes — Tue, 05 Jun 2012 22:30:00 GMT

This weekend was the Day of DotNetNuke in Charlotte, NC . I was there to present two session, along with three other Engage colleagues ( Oliver Hine and Anthony Overkamp also presented). I was honored to be able to present on the Client Resource...(read more)

DNN World 2011

bdukes — Mon, 14 Nov 2011 14:45:56 GMT

We’re on the plane flying back to St. Louis from DNN World 2011 . I gave a presentation titled DNN 6 UI/UX Patterns , discussing the form patterns introduced in the administrative modules in DNN 6 (the new look and feel that you immediately noticed...(read more)

JavaScript: true, false, and in between

bdukes — Wed, 10 Aug 2011 13:58:00 GMT

In JavaScript, all values can be coerced into a Boolean value (i.e. true or false ). Most values will evaluate to true , there are just a handful that will be false . Aside from the literal false value, the number zero ( 0 ), an empty string ( '' ), NaN...(read more)

JavaScript: this

bdukes — Thu, 30 Jun 2011 15:00:00 GMT

JavaScript is a language steeped in juxtaposition. It was made to “look like Java,” yet is dynamic and classless. From this origin, we get the new operator and the this keyword. You are probably used to this referring to the current instance of a class, so what could it mean in a language without classes?

In JavaScript, this refers to the object off of which a function is referenced when it is invoked (unless it is invoked via call or apply). What this means is that this is not bound to your function, and can change depending on how your function is invoked. It also means that this changes when declaring a function inside another function (i.e. each function has its own this), such as when writing a callback. Let's see some of this in action:

var obj = {
    count: 0,
    increment: function () {
        this.count += 1;
    },
    logAfterTimeout = function () {
        setTimeout(function () {
            console.log(this.count);
        }, 1);
    }
};
obj.increment();
console.log(obj.count); // 1
var increment = obj.increment;
window.count = 'global count value: ';
increment();
console.log(obj.count); // 1
console.log(window.count); // global count value: 1
var newObj = {count:50};
increment.call(newObj);
console.log(newObj.count); // 51
obj.logAfterTimeout();// global count value: 1
obj.logAfterTimeout = function () {
    var proxiedFunction = $.proxy(function () {
            console.log(this.count);
        }, this);
    setTimeout(proxiedFunction, 1);
};
obj.logAfterTimeout(); // 1
obj.logAfterTimeout = function () {
    var that = this;
    setTimeout(function () {
        console.log(that.count);
    }, 1);
};
obj.logAfterTimeout(); // 1

The last couple of examples here demonstrate some methods for making sure you get the values you expect. The first time logAfterTimeout is redefined, we use jQuery.proxy to create a new function which has its this permanently set to the passed in value (in this case, the current this). The second time logAfterTimeout is redefined, we save the value of this in a variable (named that in this case, also often named self) and use the new variable in place of this.

Now, all of this is to clarify what’s going on when you use this. However, it’s pretty easy to avoid using this altogether in your code (especially in the way I’ve demonstrated above). Instead of using this.count all over the place, it would have been much easier if I’d made count a variable instead of a property, and then I wouldn’t have to use this to refer to it.

var obj = (function () {
    var count = 0;
    
    return {
        increment: function () {
            count += 1;
        },
        logAfterTimeout = function () {
            setTimeout(function () {
                console.log(count);
            }, 1);
        },
        getCount: function () { return count; }
    };
}());

If you’re writing your code in this way, the main place you’ll run into issues with this is when handling DOM events (where this is the element on which the event occurred). In that case, just be careful when using a callback within that event handler, that you’re not expecting this to still refer to the element (and use proxy or that/self if you need to refer to it).

Finally, as demonstrated in the example, you can use call or apply on a function to set its this value. This isn’t often needed, but you may also want to know that you can use apply to pass in an array of arguments to a function (e.g. console.log.apply(console, [1, 2, 3, 4])).

JavaScript: Global Variables

bdukes — Tue, 14 Jun 2011 16:30:00 GMT

One of the biggest issues that you can run into with writing JavaScript is abusing the shared global namespace, and overwriting the variables of an unrelated script. Everything that you declare in JavaScript is available to every other script on the page...(read more)

JavaScript Functions

bdukes — Thu, 09 Jun 2011 16:25:00 GMT

When coming from a strongly-typed, object-oriented background, there may be some surprising elements when looking at how functions are used in JavaScript. Functions in JavaScript don’t have any real concept of a signature, like they would in .NET. All...(read more)

Why isn’t My Scheduled Task Executing?

bdukes — Wed, 08 Jun 2011 15:39:49 GMT

A quick diversion from the JavaScript Common Difficulties and Misconceptions series (I have another post queued up, just need to write the sample code), for an issue I just ran into. Created a scheduled task for DNN, but it’s sitting in the scheduler...(read more)

Closure and Scope

bdukes — Tue, 31 May 2011 14:30:00 GMT

The term closure refers to a function which references variables outside of its scope; the function is “closed over” those variables. I’ll give an example of misusing closure in JavaScript and C#, then compare the solutions. This example is going to attempt...(read more)

JavaScript: The Language

bdukes — Tue, 24 May 2011 13:05:57 GMT

I gave my JavaScript language talk at the St. Louis .NET/DotNetNuke User Group last night. I’ve posted the presentation (with some updated, clarified example code) up on slideshare. JavaScript: The Language I woke up this morning thinking through...(read more)

Escaping Commas in ReSharper Live Templates Comma-Delimited Macros

bdukes — Mon, 21 Feb 2011 21:46:43 GMT

ReSharper is an irreplaceable tool in my coding arsenal. One of its myriad of amazingly useful tools is Live Templates , a much enhanced version of Visual Studio’s code snippets. When defining a live template you can specify a number of placeholders...(read more)

Chicago Day Of DotNetNuke 2010 Recap

bdukes — Tue, 12 Oct 2010 14:00:47 GMT

Saturday, October 2nd was the Day of DotNetNuke in Chicago . A number of us from Engage attended and spoke . I gave two presentations, which are now available on SlideShare (linked below). I’ve added some notes (be sure to click the...(read more)

My Messages Inbox: A Mobile DotNetNuke Application for the St. Louis DNN Hackathon

bdukes — Mon, 30 Aug 2010 17:24:06 GMT

This past week was the St. Louis DotNetNuke Hackathon . This was a competition for DNN developers to create a mobile application which interacts with DNN . We had one week to create something worth showing off. So, I, along with another...(read more)

New Helper Methods in .NET 4 (or, A Great New Method With a Caveat)

bdukes — Wed, 03 Mar 2010 15:28:00 GMT

On Twitter yesterday, Brad Abrams mentioned String.IsNullOrWhiteSpace , to awesome new helper to replace compliment String.IsNullOrEmpty . I'm really excited to get to use this, since it seems like it makes more sense in the majority of cases than IsNullOrEmpty...(read more)

DotNetNuke & MVC

bdukes — Thu, 28 Jan 2010 15:36:00 GMT

Earlier this week, Shaun Walker, DotNetNuke 's Co-Founder and Chief Architect, caused a bit of a ruckus in the blogosphere/twitterverse with his blog post ASP.NET MVC and DotNetNuke . I think many disagreed with his representation of ASP.NET MVC, whether...(read more)