Computer Programming

JavaScript Objects: Prototype

2009-04-15T00:31:00.000-07:00

prototype

• A prototype is a property of every JavaScript object
• Functions and properties can be associated with a
constructor's property
• When a function is invoked with new keyword, all
properties and methods of the prototype for the
function are attached to the resulting object46

// Constructor of the MyObject
function MyObject(name, size){
this.name=name;
this.size=size;
}
// Add a function to the prototype
MyObject.prototype.tellSize=function{
alert(“size of “ + this.name+” is “ + this.size);
}
// Create an instance of the object
var myObj=new MyObject(“Sang”, “30 inches”);
myObj.tellSize();

PHP Variable

2009-04-15T00:25:00.000-07:00

PHP variable syntax $a , $b.

Not Different in this variable

example :

<?php

$a = 1;
$b = 2;

$c = $a + $b;

echo "$c";

?>

Getting Started With PHP

2009-04-15T00:21:00.000-07:00

PHP programming starting code <?php end finished ?>

example :

<?php

echo "Hello Word";

?>

JavaScript Events

2009-04-14T23:58:00.000-07:00

Events & Event Handlers

Every element on a web page has certain events

which can trigger invocation of event handlers

Attributes are inserted into HTML tags to define

events and event handlers

Examples of events

> A mouse click
> A web page or an image loading
> Mousing over a hot spot on the web page
> Selecting an input box in an HTML form
> Submitting an HTML form
> A keystroke

Events

• onabort - Loading of an image is interrupted
• onblur - An element loses focus
• onchange - The content of a field changes
• onclick - Mouse clicks an object
• ondblclick - Mouse double-clicks an object
• onerror - An error occurs when loading a document
or an image
• onfocus - An element gets focus
• onkeydown - A keyboard key is pressed
• onkeypress - A keyboard key is pressed or held down
• onkeyup - A keyboard key is released
• onload - A page or an image is finished loading
• onmousedown - A mouse button is pressed
• onmousemove - The mouse is moved
• onmouseout - The mouse is moved off an element
• onmouseover - The mouse is moved over an element
• onmouseup - A mouse button is released
• onreset - The reset button is clicked
• onresize - A window or frame is resized
• onselect - Text is selected
• onsubmit - The submit button is clicked
• onunload - The user exits the page
onload & onUnload Events
• The onload and onUnload events are triggered when
the user enters or leaves the page
• The onload event is often used to check the visitor's
browser type and browser version, and load the
proper version of the web page based on the
information
• Both the onload and onUnload events are also often
used to deal with cookies that should be set when a
user enters or leaves a page.
onFocus, onBlur and onChange
• The onFocus, onBlur and onChange events are
often used in combination with validation of form
fields.
• Example: The checkEmail() function will be called
whenever the user changes the content of the field:
<input type="text" size="30"
id="email" onchange="checkEmail()">;

Example & Demo: onblur

<html>
<head>
<script type="text/javascript">
function upperCase() {
var x=document.getElementById("fname").value
document.getElementById("fname").value=x.toUpperCase()
}
</script>
</head>
<body>
Enter your name:
<input type="text" id="fname" onblur="upperCase()">
</body>
</html>
onSubmit
• The onSubmit event is used to validate ALL form
fields before submitting it.
• Example: The checkForm() function will be called
when the user clicks the submit button in the form. If
the field values are not accepted, the submit should
be cancelled. The function checkForm() returns
either true or false. If it returns true the form will be
submitted, otherwise the submit will be cancelled:
<form method="post" action="xxx.html"
onsubmit="return checkForm()">

Example & Demo: onSubmit

<html>
<head>
<script type="text/javascript">
function validate() {
// return true or false based on validation logic
}
</script>
</head>
<body>
<form action="tryjs_submitpage.htm" onsubmit="return validate()">
Name (max 10 chararcters): <input type="text" id="fname" size="20"><br />
Age (from 1 to 100): <input type="text" id="age" size="20"><br />
E-mail: <input type="text" id="email" size="20"><br />
<br />
<input type="submit" value="Submit">
</form>
</body>
</html>

onMouseOver and onMouseOut

• onMouseOver and onMouseOut are often used to
create "animated" buttons.
• Below is an example of an onMouseOver event. An
alert box appears when an onMouseOver event is
detected:
<a href="http://www.w3schools.com"
onmouseover="alert('An onMouseOver event');return false">
<img src="w3schools.gif" width="100" height="30">
</a>

JavaScript Variable

2009-04-14T23:56:00.001-07:00

• You create a variable with or without the var
statement
var strname = some value
strname = some value
• When you declare a variable within a function, the
variable can only be accessed within that function
• If you declare a variable outside a function, all the
functions on your page can access it
• The lifetime of these variables starts when they are
declared, and ends when the page is closed13
JavaScript Popup Boxes
• Alert box
> User will have to click "OK" to proceed
> alert("sometext")
• Confirm box
> User will have to click either "OK" or "Cancel" to proceed
> confirm("sometext")
• Prompt box
> User will have to click either "OK" or "Cancel" to proceed after
entering an input value
> prompt("sometext","defaultvalue")14
JavaScript Language
• Conditional statement
> if, if.. else, switch
• Loop
> for loop, while loop
• try...catch
• throw

What is JavaScript?

2009-04-14T23:47:00.000-07:00

Was Designed to add interactivity to HTML pages

Is a scripting languange ( a scripting languange is a lightweight programming languange)

Javascript code is usually embedded directly into HTML page

Javascript is an interpreted languange (means that scripts execute without preliminary compilation)

Javascipt Funtion

2009-04-14T23:45:00.000-07:00

<html>
<head>
<script type="text/javascript">
// If alert("Hello world!!") below had not been written within a
// function, it would have been executed as soon as the page was loaded.
function displaymessage() {
alert("Hello World!")
}
</script>
</head>
<body>
<form>
<input type="button" value="Click me!"
onclick="displaymessage()" >
</form>
</body>
</html>

How and Where Do You How and Where Do You Place JavaScript Code?

2009-04-14T23:41:00.000-07:00

How to put a JavaScript code into
an HTML page?

Use the <script> tag (also use the type attribute to define the
scripting language)
<html>
<head>
<script type="text/javascript">
...
</script>
</head>
<body>
<script type="text/javascript">
...
</script>
</body>
</html>

Where Do You Place Scripts?

Scripts can be in the either <head> section or
<body> section
• Convention is to place it in the <head> section
<html>
<head>
<script type="text/javascript">
....
</script>
</head>

Referencing External JavaScript
File
Scripts can be provided locally or remotely
accessible JavaScript file using src attribute
<html>
<head>
<script language="JavaScript"
type="text/javascript"
src="http://somesite/myOwnJavaScript.js">
</script>
<script language="JavaScript"
type="text/javascript"
src="myOwnSubdirectory/myOwn2ndJavaScript.js">
</script>