JavaScript Class
Functions
A function is a reusable code-block that will be executed by an
event, or when the function is called.
A function contains some code that will be executed by an event or a call to
that function. A function is a set of statements. You can reuse functions within
the same script, or in other documents. You define functions at the beginning of
a file (in the head section), and call them later in the document. It is now
time to take a lesson about the alert-box:
This is JavaScript's method to alert the user.
alert("This is a message") |
How to Define a Function
To create a function you define its name, any values ("arguments"), and some
statements:
A function with no arguments must include the parentheses:
Arguments are variables that will be used in the function. The variable
values will be the values passed on by the function call.
By placing functions in the head section of the document, you make sure that
all the code in the function has been loaded before the function is called.
Some functions return a value to the calling expression
How to Call a Function
A function is not executed before it is called.
You can call a function containing arguments:
myfunction(argument1,argument2,etc) |
or without arguments:
The return Statement
Functions that will return a result must use the "return" statement. This
statement specifies the value which will be returned to where the function was
called from. Say you have a function that returns the sum of two numbers:
When you call this function you must send two arguments with it:
The returned value from the function (5) will be stored in the variable
called sum.
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