In many other interpreted programming languages like: Python, PHP, ActionScript 3.0, etc., you can have defaults to arguments that do not get passed to functions. In the three a fore mentioned languages, it's as easy as saying arg = 'default' inline in the function definition. This however is not available in the JavaScript interpreter. (It might be in ECMAScript 5, though.) But that can easily be remedied with a simple helper function.

I have met other programmers that find it ridiculous that you have to create features in JavaScript that are built into other languages. They use that to put down JavaScript and call it a terrible language. However, I think that's part of what makes JavaScript so great. JavaScript, though not as powerful in features as some other languages, offers enough flexibility and expressiveness that you can create what you feel that you are missing. Lets take a look at the problem and see how easy we can remedy it.

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Many newcomers to web development may not be used to how web implementations of JavaScript execute. Namely, in what order it executes. This can be the source of many errors that are difficult to pinpoint if you aren't experienced with it. I think this also affects people who are very experienced with other programming languages and fosters a lot of undeserved hate towards ActionScript and JavaScript. (It's important to note that not all implementations of JavaScript are the same, and that some may in fact defer from what is said below. This article concerns browser and Flash based ECMAScript.)

The thing to understand about JavaScript is that it isn't compiled for the most part. (This is not exactly true for ActionScript because of the introduction of classes in ActionScript 2.0, however, the runtime script remains the same. You might argue that it compiles into a *.swf file, but in reality, that is the combination of everything that has to do with the Flash file. The ActionScript still remains live.) It's good that it isn't compiled though, because this allows for much more dynamic, expressive coding.

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In JavaScript the typeof operator reports an array as 'object'. While this is technically correct (an array in JavaScript is really just a specialized object), it's a pain in the neck when you are type checking a variable.

There are a number of ways to identify an array in JavaScript. Checking for properties of an array isn't totally accurate because you can add any named member to an object to imitate an array. Checking for 'instanceof Array' works most of the time but could be tricky in some implementations of JavaScript.

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When using multiple JavaScript libraries, it is inevitable that one JavaScript file will need to call functions named in other libraries. This is necessary but can cause issues if all of the libraries aren't present.

Error handling with JavaScript is somewhat lackluster. With this in mind, you should do your best to catch and handle errors and avoid sending them to the end-user. In order to prevent errors and allow for scalability, you should test for functions that aren't present in the script where you are calling them.

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Often times when I am making dynamic scripts in Flash or JavaScript, I want to call an object method using a string. It may be a situation where I am stuck using fscommand (due to a customer request of a Flash version <8) or just writing script with script.

The problem that comes with this method is the advent of ActionScript 3 with Flash CS3/Flex 2 and the rising use in namespaces by JavaScript developers (myself included). Both encour a heavy usage of object methods instead of one-off functions. Dynamically calling singleton functions is easy, you can just use subscript notation, e.g. object[‘member/method’]. What you can’t do with this method is pass it any dot syntax and expect it to work e.g. object[‘subobject.method’]. The subscript notation is only meant to work one level. So the previous example won’t work. In order to fix this issue and to make sending object methods/members in a single string a little easier, I wrote a function that takes a string and a base object (the default is the window object if no object reference is passed) and returns the method/member. (I know at this point that some will simply direct me to ECMAScript’s built in eval() function, but I personally avoid using it at all costs as it can have unintended, and unsecure results. I’ll let Stephen Chapmen tell you because this article is about something else.)

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