Terminology
- Function: A function is a block of code that performs an action and returns a result; optionally takes arguments
-
Comment: anything following
//
on a line in JavaScript is ignored by the computer. Comments are a convenient way to leave notes in your code for yourself or other programmers.
Functions
-
alert()
opens a dialog box and returnsundefined
. -
confirm()
opens a dialog box and returns a boolean. -
prompt()
opens a dialog box and returns a string
Return Values
An argument is what you pass into a function or method; a parameter is a variable that's assigned to the argument. In the example below, number1
and number2
are parameters while 1
and 2
are arguments.
P*arts of a function*
- A function declaration starts with the
function
keyword. - Next comes the name. It should be descriptive and clear. In the example above, the name is
add
. Always use lower camel case for function names. - The name is always followed with parens. These parens may or may not include parameters. In the
add
function above,number1
andnumber2
are parameters. - The function body is enclosed in curly braces. The code inside the curly braces is the code that will be executed when the function is called.
- Generally, you will want to
return
a value from your function. It's very common for beginners to forget thereturn
, which means that the function will returnundefined
instead of a value. In the example above, theadd
function will return the value ofnumber1 + number2
.
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