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Transcript
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()
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
