CERTIFICATE IN JAVA SCRIPT -(C1099)

About the Course

JAVA SCRIPT

What is JavaScript?
History
Uses
Adding JavaScript to HTML
JavaScript syntax
JavaScript events
JavaScript classes
The HTML Document Object Model
What is JavaScript?

JavaScript is a programming language for use in
HTML pages

Invented in at Netscape Corporation
(LiveScript)

JavaScript has nothing to do with Java

JavaScript programs are run by an interpreter built
into the user's web browser (not on the server)
Where does JavaScript Fit In?

Recall
.
client opens connection to server
.
client sends request to server
.
server sends response to client
.
client and server close connection

What about Step ?
.
Client renders (displays) the response received from server

Step involves displaying HTML

And running any JavaScript code within the HTML
What can JavaScript Do?

JavaScript can dynamically modify an HTML page

JavaScript can react to user input

JavaScript can validate user input

JavaScript can be used to create cookies (yum!)

JavaScript is a full-featured programming language

JavaScript user interaction
does not require any
communication with the server
ros and Cons of JavaScript

Pros:

Allows more dynamic HTML pages, even complete web
applications

Cons:

Requires a JavaScript-enabled browser

Requires a client who trusts the server enough to run the
code the server provides

JavaScript has some protection in place but can
still cause security problems for clients

Remember JavaScript was invented in and web-
browsers have changed a lot since then
Using JavaScript in your HTML

JavaScript can be inserted into documents by
using the
SCRIPT
tag
Where to Put your Scripts

You can have any number of scripts

Scripts can be placed in the
HEAD
or in the
BODY

In the
HEAD
, scripts are run before the page is displayed

In the
BODY
, scripts are run as the page is displayed

In the
HEAD
is the right place to define functions
and variables that are used by scripts within the
BODY
External Scripts

Scripts can also be loaded from an external file

This is useful if you have a complicated script or
set of subroutines that are used in several different
documents
avaScript Variables

JavaScript has variables that you can declare with
the optional
var
keyword

Variables declared within a function are local to
that function

Variables declared outside of any function are
global variables
JavaScript Operators and Constructs

JavaScript has most of the operators we're used to
from C/Java
Simple User Interaction

There are three built-in methods of doing simple
user interaction

alert(msg)
alerts the user that something has happened

confirm(msg)
asks the user to confirm (or cancel)
something

prompt(msg, default)
asks the user to enter some text
avaScript Functions

JavaScript lets you define functions using the
function
keyword

Functions can return values using the
return
keyword
JavaScript Arrays

JavaScript has arrays that are indexed starting at 0

Special version of
for
works with arrays
Exception Handling

JavaScript also has try, catch, and throw keywords for handling JavaScript errors
Comments in JavaScript

Comments in JavaScript are delimited with // and /*
*/ as in Java and C++
avaScript Objects

JavaScript is object-oriented and uses the same method-calling syntax as Java

We have already seen this with the document object

Built-In JavaScript Objects

Some basic objects are built-in to JavaScript

String Date Array Boolean Math
JavaScript Strings

A String object is created every time you use a
string literal (just like in Java)

Have many of the same methods as in Java

charAt, concat, indexOf, lastIndexOf, match, replace, search,
slice, split, substr, substring, toLowerCase, toUpperCase,
valueOf

There are also some HTML specific methods

big, blink, bold, fixed, fontcolor, fontsize, italics, link, small,
strike, sub, sup

Don't use the HTML methods (use CSS instead)

This is the worst kind of visual formatting

JavaScript Dates

The Date class makes working with dates easier

A new date is initialized with the current date

Dates can be compared and incremented
JavaScript Arrays and Booleans

We have already seen the Array class

The Boolean class encapsulates a boolean value

.