|
Java Scripts How to write code Level 1. Place
all codes between <body></body>.
Java Scripts is a program embedded in a HTML
page. Code written between the <script></script> tag doesn't
appear on the users screen, its left for the web browser to run
the java script program. The <script></script> tag can also be
found between the <head></head> tags. Typically text that writes
text to the screen are found between the <body><body>.
First off Java Script isn't Java! Java Script
and Java have almost nothing to do with the other. Java is used
to create applets, small programs that download over the
internet and run inside web browsers. To embed Java applets
into your web pages using applet html tag. When HTML sees the
Applet tag it downloads the Java Applet from the server then
runs the specified tag when user leaves that page the applets is
dumped from memory. Java script can communicate with html
directly or Java applets and lets your write code which give a
powerful combination to your website.
Java Script is know as a snap-together
language. It is Object-oriented, "object is a type of thing
computer, car, dog etc.", each object should have a unique name
since there can be more than one like car, car1 and car3, but
typically you are encouraged to keep unique names for cars maybe
it would be The Type of Car instead of name for dogs it might be
Raven, Jack or Spot instead of dog1, dog2, dog3, etc.
Objects: have properties like dog fur, car
color, computer monitor. Java Script a window has a title and a
form a check box. Properties can modify objects and properties
can apply to completely different objects. Like each car can
have doors which would be properties but now car doors can also
become an object with its own properties, car door windows, car
door handles, etc.
Methods: What objects are able to do is called
methods. cars run, dogs play, computers crash. Java script
objects are also methods, buttons click(), text is selected(),
windows will open(). The () parentheses indicate a method rather
than a properties. For those adept in English which I am not
think of objects as nouns and methods as verbs. Objects are
things and methods are actions things which can be done, or have
been done to them.
You can put objects, properties and methods
together to describe a process or get a better description of an
object. Also known as dot syntax notice these are
separated by .'S or periods.
car.door.window
computer.monitor.cord
raven.black.male
And here are Objects and methods written in dot
syntax:
raven.plays()
computer.crashes()
car.windows.rolldown()
Events: are actions that the user performs when
at your page. Moving their mouse or pushing a button or form
submitting. Java Script deals with events with commands called
event handlers. A visitor to your page hits a button
which triggers an event handler in your script. The handlers
are;
onAbort: user aborts page load.
onBlur: user leaves the object
onChange: user changed the object
onClick: user clicks the object
onError: script encounters an error
onFocus: user made an object active
onLoad: object finishes loading
onMouseOver: Cursor moves over a object
onMouseOut: mouse moves off of a object
onSelect: user selects the contents of a object
onSubmit: user submitted a form
onUnload: user left the window.
as the user triggers an event handler lets say
now a
car handles the event onWindowDown() performing the action
window down
Values & Variables: a piece of information in
Java Script is known as a value. there are two types numbers &
string value (or text enclosed in "" quotes), Variables contain
values the variable MyCarColor is assigned the string "Yellow"
another way to write this is myCarColor="yellow". the = means is
assigned to. so now the variable name myCarColor is now set to
yellow.
Java Script is Case Sensitive Upper Case vs.
lower case makes a difference.
Value Types:
Number: any number value i.e... 2.155556565
String: Characters inside the "" quotes. i.e.... "hello,
EyeTweaks!"
Boolean: true or false
Null: empty or no value typically 0 or blank space
object: value associated with the object
function: value returned by a function.
Operators: are symbols used to work along with
variables.
Operators:
s + t(number) adds x & y together
s+t(string) adds text x & text y together ie x=Eye
& y=Tweaks =EyeTweaks
s-t subtracts y from x
s*t multiples x times y
s/t divides x by y
s%t Modulus or the remainder when x is
divided by y
s++, ++s adds one to x same as x=x+1
s--, --s subtracts on from x same as x=x-1
-s reverses the sign on x
now s++ & ++s are not the same the first
increment s is after the assigned is completed and before the
last s so if s is equal to 1 s=s++ this value would be 1 so s=1
and t=++s is set to 2 it will result in both operators being set
to 2 instead of the first one on = to 1 it is now both equal to
2. the -- operators work the same way. If you mix numeric and
strings together like "dog" + 9 you will get dog9.
Assignments & Comparisons: when you place a
value in a variable you are assigning the value to the
variable. You will use what is called an assignment operator to
do the job. example is using a = equal operator to do
assignement like carColor="Yellow". another way of saying s=s+6
is s+=6. Comparisions to compare one value to another, like the
time of day or day of week do this by checking if todaysDate
=="Monday" or greater than and less than when comparing strings
remember that "a" is greater > than "A" and Alan is less < than
Sunshine.
Assignments:
s = t sets s to the y value
s += t same as s = s + t
s-=t same as s=s-t
s*=t same as s=s*t
s/=t same as s=s/t
s%=t same as s=s%t
Comparisons:
s==t returns true if s and t are equal
s!=t returns true if s and t are not equal
s>t returns if s is greater than t
s>=t returns true if s is greater than or equal to t
s<t returns true if s is less than t
s<=t returns true if s is less than or equal to t
s&&t returns true if both s and t are true
s||t returns true if either s or t is true
!s returns true if s is false
To write Java Script you need nothing more than
word or notepad on Mac it might be simple text, personally I use
front page and program directly into the file. Almost any text
editor will work for this. Java Script is really just plain
text. When you use your text editor just save the files with
the extensions .htm or .html so your browser can read them once
you have uploaded to your site.
Ok now you know the basics learn that little
practice the rest will come easy.
Member of the EyeTweaks Network, We just keep on Tweaken!TM
CoolDisks.com All copyrights apply.(C) |
|
Contact Us
| 
Batch
