Who knows who develops any of the functions function () is that they have or fewer of input arguments. It can happen sometimes, having to write a function that, based on input parameters, it behaves differently (in OO programming we find this behavior indicated as polymorphism). Variable parameters (varargs), already introduced at the time of C is present by default in the classic statement of the main

not be confused with the default setting of a parameter, also now fully supported Actionscript 3.0.

Default Arguments

For example in PHP you can define a function like this:

the parameter $b is optional, that is, if not passed during the call to assume the default value of 5.

As anticipated Actionscript 3.0 also now fully supports this system:

ActionScript 3.0 was introduced the ability to declare default parameter values for a function. If in a call to a function with default parameter is omitted a parameter with default values, use the value specified for this parameter in the function definition. All parameters with default values must be placed at the end of the list of parameters. The values assigned by default to be constants at compile time. The existence of a default value for a parameter means that the parameter becomes an optional parameter, while a parameter with no default value is considered a required parameter.

The same goes for PHP: a parameter with a preset value venta optional.

In ActionScript 3.0, similar to the example shown above in PHP, you can preset the input parameters this way:

Even in this case the second parameter b automatically becomes optional.

In JavaScript, unfortunately, this feature is not - yet - supported. Although there are some "convoluted" techniques (see for example Default Arguments in JavaScript Functions) to simulate or bypass the obstacle, the use of this technique in Javascript is very limited.

Variable parameters

This technique, unlike its predecessor, allows you to examine the content and the presence of the input parameters of a function. It is evident that this approach may also be used to set parameters missing. In PHP, for example, we have three simple functions that operate on the input parameters: func_num_args() func_num_args() and func_get_arg() These functions allow respectively to return the number of arguments, return an array with all elements of input, retrieve a specific element of input. Eg

Returns the number of arguments passed to the function pluto In the example below, however, is seen as a task can vary its behavior based on the number (and also the type - polimofica) of its parameters. In this case if we call pluto() with two or more parameters is displayed otherwise not.

This allows you to "simulate" a default setting of parameters, but since PHP supports native and still more convenient that set out above. However here is an example to clarify:

or:

In Actionscript and Javascript have a situzione like:

in Javascript:

Since ECMA, Actionscript and Javascript are very much alike, using both an object arguments which then provides various information.

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