Function.prototype 391
In almost all cases, the function call operator (()) can be used instead of this method. The
function call operator produces code that is concise and readable. This method is primarily useful
when the
this parameter of the function invocation needs to be explicitly controlled. Normally,
if a function is invoked as a method of an object, within the body of the function,
this is set to
myObject as in the following:
myObject.myMethod(1, 2, 3);
In some situations, you may want this to point somewhere else; for example, if a function must
be invoked as a method of an object, but is not actually stored as a method of that object.
myObject.myMethod.call(myOtherObject, 1, 2, 3);
You can pass the value null for the thisObject parameter to invoke a function as a regular
function and not as a method of an object. For example, the following function invocations
are equivalent:
Math.sin(Math.PI / 4)
Math.sin.call(null, Math.PI / 4)
Example
This example uses Function.call() to make a function behave as a method of another object,
without storing the function in the object.
function MyObject() {
}
function MyMethod(obj) {
trace("this == obj? " + (this == obj));
}
var obj = new MyObject();
MyMethod.call(obj, obj);
The trace() action sends the following code to the Output panel:
this == obj? true
Function.prototype
Availability
Flash Player 5. If you are using ActionScript 2.0, you don’t need to use this property; it reflects the
implementation of inheritance in ActionScript 1.
Usage
myFunction.prototype
Description
Property; in an ActionScript 1 constructor function, the prototype property refers to an object
that is the prototype of the constructed class. Each instance of the class that is created by the
constructor function inherits all the properties and methods of the prototype object.
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