Question

What is the difference between calling exampleFunction() and exampleFunction.call() ?
There is a feature on Actionscript that allows you to use functions through the ‘call’ method. For example, to use the ‘test’ function below, I could write test() and test.call()

function test():void {
 trace('function was called')
}

What is the difference?

Answer 1

As with ECMAScript (from which AS is derived) it allows specifying the “this” context via the first parameter.

See the Function.call documentation. Note the remarks about functions vs. methods – or “bound functions” – and the examples.

That is, given:

function f ():* { return this; }
var x:Object = {f: f};

Then:

Both f.call(x) and x.f() evaluate to x while f() does not as it has a different “this” (it evaluates to Global instead).

If f.call() (no params) is used then “this” will be NaN while f(), as per above, has Global as “this”. Try using trace(this) in the test code as it will yield more useful contextual information.

Happy coding.