Web Application Development

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Transcript Web Application Development 

Web Application Development
Muhammad Ali
Versonic Pte
Asher Imtiaz
Forman Christian College

The Problem
 Changing the Content of Page Dynamically
 Efficient Utilization of Resources

The Solution

How?
 Scripting Languages

Interpreted Languages

Purpose
 “Automate tasks within a particular software
environment”



JavaScript
VBScript
JScript

Case Sensitive
 X != x

Few Snapshots from History
 Developed by Brendan Eich (Netscape 2.0)
 How the Name was Coined?
▪ LiveScript
▪ Renamed to JavaScript (Dec 1995 )
▪ Marketing Tactics
▪ Similarity with Java (& C++)
 Standardization Efforts
▪ ECMAScript
CSS
Flash
JavaScript
XHTML
Java
Silverlight
Communication
Flash
Java
CSS
JavaScript
HTML
Silverlight
Communication
Flash
Java
CSS
JavaScript
HTML
Silverlight
Communication
Flash
Java
CSS
JavaScript
HTML
Silverlight
Communication
Flash
Java
CSS
JavaScript
HTML
Silverlight
Communication

How to add JavaScript?
 <script type=“text/javascript”> & </script>
 Inclusion Methods
▪ Same File (HTML File)
▪ External File (JS File) ~ Preferred Approach
<html>
<head>
<script type=“text/javascript”>
alert("Hello World!");
</script>
</head>
<body>
</body>
</html>
<html>
<head>
<script>
alert("Hello World!");
</script>
<noscript>
<h1>Please enable JavaScript!</h1>
</noscript>
</head>
<body>
</body>
</html>
<html>
<head>
<script>
<!-alert("Hello World!");
// -->
</script>
<noscript>
<h1>Please enable JavaScript!</h1>
</noscript>
</head>
<body>
</body>
</html>

alert

prompt

confirm

Number
 1
 2.3

String
 “a string”

Boolean
 true
 false
 Name it and Have it!
 Use ‘var’ to declare variables!
 Examples
var num1 = 1;
var num2 = 2.3;
var str = “A String”;
var anyVar; // undefined

String Type
 To append to strings
var str1 = “abc”;
var str2 = “def”;
var strResult = str1 + str2;
 What about
var result = “1” + 2;
And
var result = “1” - 2;
And
var someVar ; // No initialization
alert(someVar);

Boolean Type
 false
▪ false, undefined, null, 0, NaN, “” (empty string)
 true
▪ Any other value is considered as true
▪ true, “abc”, 1, …

alert(typeof (1));
 number

alert(typeof(“abc”));

alert(typeof(“1”));

alert(typeof(true));

parseInt
 Converts a string to an integer number
var integerNumber = parseInt(“12”);

parseFloat
 Converts a string to a float number
var floatNumber = parseFloat(“12.12”);

Converting a Number to a String?

Loops
 For Loop
for (start; stop; step) {
action
}
Example
for (var i = 0; i < 10; ++i) {
alert(i);
}
 While Loop
boolean someCondition = true;
while (someCondition) {
// Do something
}
 Do-While Loop
boolean someCondition = true;
do {
// Do something
} while (someCondition);
Different forms

if (expr) {
// Do something
}

if (expr) {
// Do something
}
else {
// Do something
}
if (expr) {
// Do something
}
else if (expr) {
// Do something
}
else {
// Do something
}
switch (expr) {
switch (grade) {
case value1:
break;
case value2:
break;
case valueN:
break;
default:
break;
}
case “A”:
break;
case “B”:
break;
case “C”:
break;
default:
break;
}
 Objects
▪ “An object in JavaScript is a set of properties, each of which
consists of a unique name and a value belonging to one of
JavaScript’s six data types”
▪ NO Classes in JavaScript!
▪ Class-Like features.
var obj = new Object();
obj.Test = “Some Value”;
alert(obj.Test); // Some Value
delete obj.Test;
alert(obj.Test); // undefined

Enumerating Properties
for (var aProperty in obj) {
alert(aProperty + “ is a property of obj”);
}
 Displays Test is a property of obj

Accessing Properties
 obj[“Test”] = “someValue”;
for (var aProperty in obj) {
alert(aProperty + “ has value:” + obj[aProperty]);
}
var str = new String(“This is a string”);
var str = new String("abcdef");
var ch = str.charAt(0);
var index = str.indexOf("b", 0);
if (index > 0)
alert("Found at index: " + index);
else
alert("Not Found!");

split(separater, limit)

toLowerCase()
toUpperCase()
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
What’s an Array?
 var ar1 = new Array();
 var ar1 = new Array(5);
 var ar2 = new Array(4, true, “OK”);
 var ar3 = [4, true, “OK”];
 var twoDimAr = [
[ “X”, “O”, “O”],
[ “O”, “X”, “O”],
[ “O”, “X”, “O”]
];

Access an Element at Index ‘i’
 ar[i] = 12;
 alert(ar[3]);

toString

splice

reverse

length

push

Math
 abs, ceil, floor, round, random, …
 Trigonometric, logarithmic, etc

Date
 Dates before January 1, 1970 are not supported

What have we learnt today?
 Need for client side programming
 Why scripting languages?
 JavaScript for client side programming
 Language features of JavaScript