The Arguments Object
In each function call there is created for it, in the local scope of that call, an object called arguments. The arguments itself is really just an array. It contains all of the values that were passed in to the function when it was called. For example, in the function call

myFunction("A", 2);

myFunction receives 2 arguments, the letter "A" and the number 2. In the body of that function, arguments would be an array with arguments[0] containing "A" and arguments[1] containing 2.

myFunction = function(){

trace(arguments[0]); // traces "A"

trace(arguments[1]); // traces 2

};

myFunction("A", 2);

Aside from providing the arguments of the function call, the arguments object also has 2 other properties, callee and caller.

Arguments.callee represents the function object running call. Arguments.caller is one up on callee representing any function (if there is one) calling the callee. If a function was not run from another function then there is no caller and arguments.caller will be null. Arguments.callee will always exist though, as to run a function, there obviously needs to be a function. Arguments.callee represents the this of the function object itself. Consider the following example.

tracePhrase = function(){

trace(arguments.callee.phrase); // traces "Phrase accessed through callee"

};

tracePhrase.phrase = "Phrase accessed through callee";

tracePhrase();

The phrase property was added directly to the tracePhrase function. Accessing its value means using arguments.callee to get to the tracePhrase function object itself. Granted, you could use tracePhrase directly, but what if you don’t know the name of the function?

Callee is for the function calling the function.

runTracePhrase = function(){

tracePhrase();

};

tracePhrase = function(){

trace(arguments.callee.phrase); // traces "Phrase accessed through callee"

trace(arguments.caller == runTracePhrase); // traces true

};

tracePhrase.phrase = "Phrase accessed through callee";

runTracePhrase();

Since runTracePhrase is the function that called tracePhrase, arguments.caller in tracePhrase is a reference to the runTracePhrase function. Though the arguments is a powerful and helpful object on a whole, I can’t say arguments.caller is used often so don’t worry if you forget what it means.

And that’s about it for object basics. Now its time to get into the creation of custom objects and custom classes.

For more on scope, see Timothée Groleau’s in depth article Scope Chain and Memory Waste in Flash MX.

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