Declaring Va ?les and Func ? ?ont>
< ?ign="lef ? Adding ?able ?d functions ?our ? ?/span>
Now it's time to get into some reall ?n st ? Yes, va ?les and func ? ?on't wor ?it's not as bad as i ? ?.....let's s ? with declaring ?able ?ou'll want to keep all of yo ?ariables in ?HEAD sec ? for now. Place ?declarations ? the SCRIPT ? inside ?head sec ? of ? doc ? ?/fon ? ? To decla ? variable in JavaScript, you will write ? ?g like this:
< ?ign="lef ?&l ?AD>
<SCRIPT language="JavaScri ?
<!--hide from old bro ? ? ?
?name=val ?
//--&g ? ?
</SCRIPT>
</HEAD> Here is ? the ?ommands mean:
- var
name
This is ?name you give the va ?le. Give it any name you like (o ? than a JavaScri ?eser ? ? such as "function" or "onMo ? ?.).
value
This is ?initial ?e yo ?nt the variable ?ave. It can be a number, words, ?, false, or null.
< ? cla ?heading">Using N ? ? ?>
You can assign a number ?e to a variable by placing the desired n ? ? ? ?= sign:
var cars=3; You can also use a n ? ? ? decimal. Ja ? ? isn't too picky abo ?hether the value is an integer o ?cimal. J ? ? it in.
align="left"> var cos ?95;
U ? Strings
A ?ng i ? ? gro ?f charac ?, such a ? ?ence or a wo ?To define a ?ng, ? ? need to place single or double ?e ma ?around the value, like this: ?movie="The Lost World";
Also, if yo ?ace numbers inside the q ? ?hey are ? ?as a string ?er than a numerical ?e. Boolean Values
This one i ?ce. Assign the variable a value of t ?or false. No quo ?needHere's an example:
< ?ign="lef ?font color="#FFFFFF"> va ?ory= ?;
< ? cla ?heading">The null Value
If ?declare ? ?g as null, i ?ans nothing. Not even ze ?just plain nothing. Here's the forma ?/fon ?div>
< ?ign="lef ?font color="#FFFFFF"> va ?mone ?ll;
Well, nothingne ? ? so grea ? thi ? ?but it can be useful when yo ?e prompt ? get informa ? from viewer ?nd they ? in......nothing!
< ? cla ?heading">Case Sensitivit ? ?
Unlike alot of things in HTML, Ja ? ? ?e ca ?ensi ?. Soariable named "john" is not ? ? as "John" o ?OHN". The same goes for commands and functions and so on. Ju ?emember ? case when you u ?avaScrip ?or you may get e ? cit ? ?d of nif ?ffec ?..
Semicolo ?>
Don' ? ? tho ?emicolon ?hey are ? to ? ? JavaScript commands and declara ? ?nd can also cause er ?city if ? are lef ?f. I did thi ?few ? ?nd i ?kes for ? pre ? ? stuff when ? ? ?oad ? ?!
F ?ions!
Well, functions a ? ? ?ake ?gs more organized and readable. A function i ? ?of JavaScrip ?atements put togethe ? ? ?le p ? ?You ? wan ? kee ? ? ?ions inside ?PT tags inside the HEAD ?ion. Here is the format for a function decla ?on:
<HEAD>
<SCRIPT language="JavaScript">
function name ( ?mete ? ?mete ?
{
JavaScri ? ?ment ?d declarations
? ?
//-->
</SCRIPT>
</HEAD>
func ?
Indicates that ?are going to create a function.
-
i>
name
Thi ? the name yo ? ?he f ?ion. As befo ?name it ?ever you like.
< ?ign="lef ?
-
(pa ? ?, pa ? ?)
-
{
This symbol lets you begin adding Ja ? ? sta ?nts and declarations.
-
?>
This indicates the end of ? ?emen ?and ?end of the f ?ion.
< ?ign="lef ?font color="#FFFFFF"> To make use of the function, you will make a c ?he f ?ion ? you wan ? use it. You call a func ? by ?g the name, any ?mete ?ou want ?end, and a semicolon, like this:
< ?ign="lef ?font color="#FFFFFF"> function dosomething (mymoney, cos ?
Place ? mou ?ere!
< ?ign="lef ?font color="#FFFFFF"> No ?ere' ?e code that gene ?d the link. See if you can work ? way through it. I'll ex ?n it at ?end of the scrip ? ? ? <HEAD>
&l ?-hide
? ?=" ";
func ? ove ?k (text)
{
window. ? ?ext;
}
function offlink (t
{
window. ? ?ext;
}
//-->
</SCRIPT>
</HEAD>
&l ?DY>
<A HREF="java7.ph ?nMou ?er="overlink('Functions Rule!'); ? ? ?
onMouseout="offlink(' ');return tr ? Place your mouse he ?lt;/A>
</BODY>
What ?..? Yes, in ? case the sc ? is much longer and ? ?me time ?ork ? ? Here's ? the script is doing:
< ? cla ?heading">In ?HEAD Sec ?
-
-
func ? ove ?k(te ?/b> declare ?func ? named o ?ink. The function re ?es the variable ? to be sent ? ? order to wo ? ? ?
{
Beg ?JavaScri ? ?ment ? ?e function o ?ink.
windo ?atus=tex ?b>
?>
Ends the s ?ment ? the function overlink.
function offlink ( ?)
This decla ?a function named offlink. The function requi ? ? ?able tex ? be ? to it in order ?ork ?erly.
?ow.s ? ? ?br />
This places ? ?e of the variable te ?n the status bar. The value of text ? ? to ?func ? when it was called inside the link ? which i ?e st ? " ". See the ex ?nation of the link tag for more.
h3 align="left">In the BODY Section
<A HREF="jvar.php" onMouseove ? ?ink('Functions R ?');return tr ?
onMouseout="offlink(' ');re ? true"> Place yo ?ouse here!&l ?>
< ?ign="lef ?font color="#FFFFFF"> This tag calls both of the functions and passe ? a s ?g which is a ?ned ?he variable named te ?The firs ?nction, overlink, is called inside the onMou ?er command. This means that ? the use ?aces their mouse ove ?e link, ? ?emen ?nside the function o ?ink ? be exec ?. As you can see, overlink i ?lled with a ?ng variable inside the ( ) s ?ls. Notice we use single quo ? ?efine this s ?g, since double ?es a ? ?in the onMou ?er command. The ?ng value we ?e he ? ?at i ?nt to the function o ? and thu ? wha ?ds u ? the sta ?bar. So, "Functions Rule!" i ?at shows up in the s ? ? ?en the mouse moves o ? ?link. The onMouseout command calls the f ?ion named offlink when the mouse moves a ?from the link. This ?, we assigned the va ?le text a value of blank space. The blank space is sent ?he f ?ion, and is ? ? ?he s ? ? ? ?ng the "Func ? ?le!" string befo ? ?he return tr ?hrases a ?here to make sure the sc ? works b ? ?ing ?.
Well, if ?made it ? ?all of that, you are ready to mo ?n. If yo ?ill don' ?have a handle on it ? try wri ? out the script on your comp ?, or even by hand. Sometimes it help ? ? ?our ? ? ? ?mess ? ?
< ?ign="lef ?font color="#FFFFFF"> Well, let' ? ?n to some mo ?echnical stuff, in the next ?ion:
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