How to write text on a page.
<html>
<body>
<script type="text/javascript">
document.write("Hello World!")
</script>
</body>
</html>
Write text with formatting
How to format the text on your page with HTML tags.
<html>
<body>
<script type="text/javascript">
document.write("<h1>Hello World!</h1>")
</script>
</body>
</html>
How to Put a JavaScript Into an HTML Page
<html>
<body>
<script type="text/javascript">
document.write("Hello World!")
</script>
</body>
</html>
The code above will produce this output on an HTML page:
Hello World!
Ending Statements With a Semicolon?
With traditional programming languages, like C++ and Java,
each code statement has to end with a semicolon.
Many programmers continue this habit when writing JavaScript,
but in general, semicolons are optional! However, semicolons
are required if you want to put more than one statement on a
single line.
How to Handle Older Browsers
Browsers that do not support scripts will display the script as page
content. To prevent them from doing this, we may use the HTML comment
tag:
<script type="text/javascript">
<!--
some statements
//-->
</script>
The two forward slashes at the end of comment line (//) are a JavaScript comment
symbol. This prevents the JavaScript compiler from compiling the line.
Note: You cannot put // in front of the first comment line (like //<!--),
because older browsers will display it. Strange? Yes! But that's the way it
is.
Scripts in the body section will be executed WHILE the page loads.
Scripts in the head section will be executed when CALLED.
The alert, confirm, and prompt boxes
The three "commands" involved in creating alert,
confirm, and prompt boxes are:
- window.alert()
- window.confirm()
- window.prompt()
Lets look at them in detail:
The first one is:
window.alert()
This command pops up a message box
displaying whatever you put in it. For example:
<body>
<script>
window.alert("My name is Bob. Welcome!")
</script>
</body>
As you can see, whatever you put inside
the quotation marks, it will display it.
The second one is:
window.confirm()
Confirm is used to confirm a user
about certain action, and decide between two choices depending
on what the user chooses.
<script>
var x=window.confirm("Are you sure you are ok?")
if (x)
window.alert("Good!")
else
window.alert("Too bad")
</script>
First of all, "var x=" is a
variable declaration; it declares a variable ("x" in this case)
that will store the result of the confirm box. All variables
are created this way. x will get the result, namely, "true" or "false".
Then we use a "if else" statement to give the script the ability
to choose between two paths, depending on this result. If the
result is true (the user clicked "ok"), "good" is alerted. If
the result is false (the user clicked "cancel"), "Too bad" is
alerted instead. (For all those interested, variable x is called
a Boolean variable, since it can only contain either a value
of "true" or "false").
The third one is:
window.prompt()
Prompt is used to allow a user to
enter something, and do something with that info: