JavaScript Tutorial: JavaScript Functions and Methods
Functions and methods are pretty much the same thing.
However, you write functions that include event handlers, variables, and
statements. In previous examples we saw a simple method, document.write.
Document is the object, and write is the method. Functions are a little more
detailed.
Look at the following piece of code:
| <a href="#" onClick="alert('Three plus two is '
+ addNumbers(3,2)); return false;">Add 3 + 2</a> |
This piece of code would cause a small alert box to pop
up on the screen that says Three plus two is 5. Note the # sign in the href
tag. This is basically used as a place holder, because we want to use a link,
but we don't want that link to go anywhere. Also note that we have return
false there, which tells the browser not to perform its default action when
the link is clicked, which would normally be to take you to another page.
All of this together is a function.
You can also use a function like this:
function popup()
{ alert('This is a popup'); } |
In this example, you have actually specified that a function
is being called, and the function is to popup an alert box that says This
is a popup.
JavaScript functions are not loaded until they are called or until the user
performs a certain action. Functions are placed in the HTML code in the
<head></head> section. They can also be linked to in the head
section if they are on a separate document.
Here is another example:
<html>
<head>
<script type="text/javascript">
function displaymessage()
{ alert("Welcome!") }
</script>
</head>
<body>
<form>
<input type="button" value="Click Here!" onclick="displaymessage()"
>
</form>
</body>
</html> |
Here we have placed a function in the
<head></head> section of a webpage, and a button in the body
of the web page that says Click Here. When this button is clicked by the
user, an alert box will popup that says Welcome. Notice that after we write
function, we use the displaymessage ( ). We state that we want to perform
a function, and then define what that function is.
You will learn to use many different types of functions and methods as you
go along. You don't have to memorize all of them.
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 JavaScript Tutorial: An Introduction
to JavaScript
The Basics of
JavaScript
JavaScript
Events
JavaScript
Variables and Arrays
JavaScript
Statements
JavaScript
Functions and Methods
JavaScript
Errors
JavaScript Food
Chain
Writing JavaScript
Code
JavaScript
Object Reference
JavaScript
Events Reference
JavaScript
Functions Reference
JavaScript
Math Object Reference
JavaScript Array Object
Reference
JavaScript String Object
Reference
JavaScript
Date Object Reference
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