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Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
3
Competencies
At end of unit be able to » Describe 3 times when javascript runs» Describe some of the capabilities of JavaScript» Write a JavaScript with conditional expression» Use a JavaScript program with variables and
calculations
Competency Alert:You need to
know this!
Common Problem Area!
People seem to forget this
4
JavaScript: Its Beginnings JavaScript developed by Netscape & initially called livescript. After Java came out, Netscape cut a deal with Sun to rename
it to JavaScript (12/95). » They are separate, distinct languages. (Though JavaScript is simpler).
Microsoft … » Came out with their own flavor of JavaScript called “Jscript”.» They also added support for VBScript in IE. Differences are minor.
Eventually standardized … » JavaScript has been turned over to the European Computer
Manufactures Association, and is now officially called ECMAScript» Both Netscape & IE4.0 and Netscape implement ECMAScript
standard.
5
The “goods” on JavaScript
JavaScript can be used to: 1. perform simple client-side computations
For example, add up total costs of shopping cart before it is submitted.
2. facilitate dynamic and interactive Web page creation For example, do image roll overs, pop up windows
on click, expand a menu.3. Verify HTML forms enhance HTML forms with data
collections and form validation 4. manipulate user cookies -
6
The “not so goods” on JavaScript
JavaScript runs completely on Client machine It does NOT have:
1. Any graphic capabilities E.g., cannot show a graph of survey results.
2. Access to client (you PC) resources Cannot print, modifying PC files, or launching client
applications.3. Access to any Web server resources
E.g., cannot send email, write to file, write to database.
7
PHP/JavaScript Similarities and Differences
What they have in common. Both languages can:1. Be embedded in HTML documents2. Cause dynamic content to be displayed (e.g., the current date)3. Can be placed in external files and “included” into html files4. Look more like a programming language than HTML
What they DON’T have in common: 1. The big difference … JavaScript runs 100% on client (i.e., PC). This
means:A. JavaScript stuff runs noticeably faster
(not dependent on Internet and Web Server)B. PHP has access to Web Server resources (mail, databases, files)
2. Using differencesA. Writing JavaScript does NOT require a Web Server (but more
concern about browser implementation differences).B. PHP’s syntax is easier to write and understand for beginners.
8
How JavaScript Pages are Run
2. Send Request for PHP file
6. Return Results
Please EnterAPhoneNumber
Submit Erase
1. Web Browser
Web Browser
Phone QueryResults:
That isJohn Doe'sPhoneNumber
7. Web Browser
Your PC(Internet connected)
WebServer(Internet connected)
Web ServerSoftware
3. Receiverequest, find
file and read it.
4. ExecutePHP
statements
5. Sendresultsback.
JavaScript does not run here
JavaScript is run here by the browser but just before HTML
9
Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
10
Adding JavaScript to HTML pages
JavaScript is added to HTML pages using the <script> tag.• usually placed in the HEAD or BODY of the document
<script src=URL language=“JavaScript”></script>
<script language=“JavaScript”><!--
Javascript code//--></script>
If link to an external file (use .js suffix)
If embed JS within HTML
11
A Simple Example<HTML>
<HEAD> <TITLE> A Beginning Script </TITLE> </HEAD> <BODY> <SCRIPT LANGUAGE="JavaScript"> document.write ("Welcome to the wonderful world of JavaScript"); </SCRIPT> </BODY> </HTML>
These statements are run before HTML document interpreted by browser
Within the javascript ‘mode’ any output to browswer needs to be within a document.write output command
12
Where do you put it?
•Can add JavaScript to head or body of html document
•Functions are usually added to the head section • assures that the functions OK (parsed) by the time they are called.
•Non-functions usually put in body then can call and functions in head
13
Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
14
When does it run?
JavaScript can run1. as the page loads2. as soon as the page is finished loading3. in response to user input (remember the form
button?)
Competency Alert:You need to
know this!
15
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><CENTER><H2>Document Object </H2><SCRIPT language=JavaScript> document.write("This page was last modified on” + document.lastModified);</SCRIPT></CENTER></BODY></HTML>
JavaScript that Runs as Page Loads
Enter JavaScript. Within thehtml body (in this case)
Normal HTML code
document.write like print. Get lastModified browser vrbl. . The + is catenation.
Calls function to get current date and output date
document.write("This page was last modified on” + document.lastModified);
Output this set of text (called a string) Output the result of this ‘command’
16
JavaScript output (onload) is HTML
input … . The output of JavaScript statements is taken as HTML input...
<HTML> <HEAD><TITLE> A Beginning Script </TITLE> </HEAD><BODY> <SCRIPT language=JavaScript> document.write ("<FONT Size=4>JavaScript commands are interpreted
first</FONT>"); document.write ("<BR> <FONT COLOR=BLUE>JS output often generates HTML</FONT>"); </SCRIPT></BODY></HTML></HTML>
Write these 2 messages
17
<html> <head> <title> Java Example 2 </title> </head> <body onload=waitLittle()><font size=4 color=blue> welcome to my page </font><br>Here is my stuff<br> <br>
<script language="JavaScript">function waitLittle(){ setTimeout( "alertMe()", 5000 );}function alertMe(){ alert('test');}</script>This is some text over here.</body> </html>
JavaScript that Runs when Loading Complete
Run ‘allertMe’ code call after 5000 miliseconds
Create a pop-up box with test as text
After 5000 milisecond pop-up
Run ‘waitLittle’ when page is loaded
18
JavaScript that Runs in Response to User Input
<html><head><script language="JavaScript"><!--function showTime(){ document.forms["getDate"].curTime.value = (new Date()).toLocaleString();}function alertme(){ alert("Don't Do that");}//--></script></head><body style="background-color: #fffff0;"><form name="getDate"><input type="button" name="getTime" onClick="showTime()" value="Show Current Time" /><input type="text" name="curTime" size="40" onClick="alertme()"/></form>
When click call showtime
Set the value of the form variable curTime to the current time
If they click generate an alert
19
Dealing with Browsers that don’t Support JavaScript
You may have noticed something a little strange about the examples so far.
<script language=“JavaScript”><!--
Javascript code//-->
</script>
This makes the script invisible to browsers that don’t support JavaScript by“commenting it out”. In addition, you can provide some page contentthat only displays when the browser DOESN’T handle JavaScript:
<noscript>Your browser doesn’t support Javascript
</noscript>
The only limitation with this is that this will NOT be displayed by NS if the userhas JavaScript just disabled.
20
Some Important Aspects of JavaScript
• Case Sensitive: Variable names, functions you use - (e.g., Date not date )
•Space Insensitive - generally ignored, except in strings•Statements end in semicolon – Except JS will assume you meant to semicolon at the end of the line if the statement appears to be complete.
21
Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
22
JavaScript And Objects ...
JavaScript is object-oriented – Objects are things your scripts can work with
Have JS objects to work with browsers, windows, and forms
– Objects have properties - are variables or other objects describing the object.
» E.g., document.lastmodified
methods - behaviors or built-in functions you use» E.g., accessed my
ObjectName.MethodName()
Object name
Object name Property has time value (like a date)
Method name
23
Using JavaScript Objects …
Lots of useful properties available Here are some properties for window object:
» document.lastModified – (read-only property) gives the document last changed date
» document.URL - (read-only property) gives the URL of the document source code file.
» window.referrer – (read-only property) gives the URL of the calling document. (It is an empty string, if user does not reach the URL by clicking a link.
» window.title – (read-only property) gives the value in the <TITLE> ... </TITLE> tag.
24
Printing out one of theseCan use the plus sign (+) to attach
string output with
propert output
document.write("last modified:”
+ document.lastModified +
"<P>");
Print out this string
Attach to the string this property
Attach to the entire string this html tag
Write the following out.
25
A couple other interesting properties
Here are a few examples of properties» navigator.appName – Set to the browser name» window.location – the current URL your viewing. Setting
this property to a URL will redirect the browser – window.location = ‘http://indelible-learning.com’;
» window.status – what is being displayed on the status line of the browser
» navigator.appName – Name of browser running» document.title – the information in the <title> tag» document.lastModified – last modified time of document
Competency Alert:You need to
know this!
26
For example <HTML>
<HEAD> <TITLE>Document Information Properties</TITLE> </HEAD> <BODY> <SCRIPT LANGUAGE="JavaScript"> document.write("Referring link was:”
+ document.referrer) + "<BR>") document.write("Document URL is:“ + document.URL +"<BR>") document.write("The title is: " + document.title +"<BR>") document. write("last modified:”
+ document.lastModified + "</P>") </SCRIPT> <HR> This is my web site. It is my Web Site all by myself. </BODY> </HTML>
27
Using an Object Method – date()
The Date object to access time and date information. Unlike the Math object, need to create a Date object first:
var dateObj = new Date();
You can specify the data/time when you create the object.
xmasObj = new Date(“December, 25, 2002”);
Can print out current date via: document.write ( new Date().toLocaleString());
Creates new date object
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><CENTER><H2>Document Object </H2><SCRIPT language=JavaScript>
document.write ( new Date().toLocaleString()); </SCRIPT></CENTER></BODY></HTML>
28
The Math Object
An example JavaScript object.
Math.abs(number)Math.sin(number)Math.cos(number)Math.round(number)Math.ceil(number)Math.floor(number)Math.log(number) Math.sqrt(number)Math.random(number)
absolute valuesine of an angle (expressed in radians)cosine of an angle (expressed in radians)closest integer valuerounds up to next integer valuerounds down to next integer valuenatural log of the numbersquare root of the numberreturns a floating point number
that is >= 0.0 but < 1.0
Other methods include:tangent, arc tangent, arc sine, arc cosine, tangent, power, angle of polar
coordinates, maximum, and minimum. Also has constant definitions for values like pi and e (natural log base).
29
Math Object Example
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY><SCRIPT language=JavaScript> document.write( "<br> sqrt(25)=" + Math.sqrt(25)); document.write( "<br> round(5.632)=" +Math.round(5.632)); document.write( "<br> floor( 5.232 )=" + Math.floor( 5.232 ));
</SCRIPT></CENTER></BODY></HTML>
30
Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
31
Using Variables
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><CENTER><H2>Using Variables </H2><SCRIPT language=JavaScript> var x = 12; var y = 15; var z = y + x; document.write( "x=" + x + "<br>"); document.write ( 'y='+ y + "<br>" ); document.write ( 'z=' + z + "<br>"); </SCRIPT></CENTER></BODY></HTML>
Set variables x, y, z
Output a string, then a variable and then <br> tag.
Common Problem Area!
People seem to forget this
Note: remember to separate strings from values with a plus sign
Competency Alert:You need to
know this!
Each variable should be ‘defined’ withvar
32
Some JavaScript Operators
Oper Example Result
+ X = 2 + z Addition - X is assigned z plus 2
+ (strg) Z = ‘a’ + ‘b” ; Catenation - Z is assigned ‘ab’
- y= 3 – 1; Subtraction – y is assign 2;
* y=2*apple; Multiplication – y is assign 2 times apple
/ x = y / 2; Division = z is assign y divided by 2.
% x = y / 2; Modulus – x is assign remainder of y/2;
-- x--; Decrement – same as x = x – 1;
++ y++; Increment – same as y = y + 1;
33
Some JavaScript Assignments
Oper Example Result
= X = 1 + 2; X is assign 3;
+= y += 2; y= y + 2;
-= z -= 1 z = z – 1;
*= X *= 2; x = x * 2;
/ = x /= 2; x = x / 2;
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><CENTER><H2>Using Variables </H2><SCRIPT language=JavaScript> x = 1; x++; x *= 2;
document.write( "x=" + x + "<br>"); </SCRIPT></CENTER></BODY></HTML>
34
Using prompt . . .
Prompt will ask the user for input and set a variable with result. . . <HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><CENTER><H2>Using Variables </H2><SCRIPT language=JavaScript> var rad = prompt('What is radius of wheel (in inches)?');
rad = parseInt(rad); var rotations = prompt('How many rotations did the wheel make?');
rotations = parseInt(rotations); var dist = 3.14 * (rad * rad) * rotations; var dist_feet = dist / 12;
document.write( "Caluating distance using a wheel of radius " + rad + " inches"); document.write( " that made " + rotations + " rotations <br>");
document.write( "distance=" + dist + " inches<br>"); document.write( "dist in feet=" + dist_feet + " feet<br>"); </SCRIPT></CENTER></BODY></HTML>
Convert character 10 to number 10
35
JavaScript Is also Event Driven
In JavaScript you can specify actions to take on many different events: » onAbort,» onBlur,» onChange, » onClick,» onDblClick,» onDragDrop, » onError,» onFocus, » onKeyDown, » onKeyPress, » onKeyUp, » onload, » onMouseDown, » onMouseOut, » onMouseOver, » onMouseUp, » onMove, » onReset,» onResize, » onSelect,» onSubmit, » onUnload
User selects a window item contents can specify some action
User puts cursor over a window item (then take some action)
User clicks a window item (then can specify some action)
User’s cursor left a window item (then can specify some action)
36
Example of a JavaScript Event
<html><head> <title> my form </title> </head> <body><script> function genAlert() { alert( "Don't do that!" ); } </script><form name="totals"> <input type="text" name="total" OnClick="genAlert()"></formm></body> </html>
When click form item thendo genalert() code.
37
Debugging JavaScript
Both Netscatpe and Firefox have built in JavaScript debug tool
From URL line type javascript:
Entering javascript: will opena JavaScript debug window
Any error messages, while script runs will show errors here
Common Problem Area!
People seem to forget this
38
Objectives Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
39
Conditionals
JavaScript has many programming constructs if ( x == 6 ) {
document.write( “6 X=“ );
document.write( x );
x += 1;
} else if ( x > 6 ) {
document.write( “LT 6 X=“ );
document.write( x );
x += 1;
} else {
document.write( “else 6 X=“ );
document.write( x );
}
document.write( “x=“ + x );
1 or more statements to run when x is equal to 6.
Test these only when x X is not 6
Run when X > 6.
Run X is not 6 or gt 6
HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><SCRIPT language=JavaScript>x=5;if ( x == 6 ) { document.write( "6 X=" ); document.write( x ); x += 1;} else if ( x > 6 ) {
document.write( "LT 6 X=" ); document.write( x ); x += 1;} else {
document.write( "else 6 X=" );document.write( x );
}document.wirte( "x=" + x );</script><H2>Using Variables </H2></SCRIPT> </CENTER></BODY></HTML>
Competency Alert:You need to
know this!
40
Example Grade Calculator<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY bgColor=#ccccff><SCRIPT language=JavaScript>var t1 = prompt( "Enter the score for the first test");t1=parseInt(t1);if ( t1 < 0 || t1 > 100 ) {
alert( "Impossible score - I cannot go on!");exit;
} var t2 = prompt( "Enter the score for the second test");t2=parseInt(t2);if ( t2 < 0 || t2 > 100 ) {
alert( "Impossible score for t2 - I cannot go on!");exit;
} var t3 = parseInt(prompt( "Enter the score for the third test"));if ( t3 < 0 || t3 > 100 ) {
alert( "Impossible score - I cannot go on!");exit;
} var aver = ( t1 + t2 + t3 ) / 3;var grade;if ( aver >= 90 ) {
grade = 'A';} else if ( aver >= 80 ) {
grade = 'B'} else if ( aver >= 70 ) {
grade = 'C'} else {
grade = 'D or lower';}document.write( 'Student average was ' + aver );document.write( '<br>This score is a ' + grade );</SCRIPT> </CENTER></BODY></HTML>
Notice how convert to number on 1 line
41
JavaScript Conditional Tests
Oper Example Result
== if ( x == 1 ) Is true if x is equal to 1
!= if ( apple != ‘blue’ ) Is true if apple is NOT equal to ‘blue’
> if ( z > y ) Is true if z is greater that y
>= if ( z >= y ) Is true if z is greater than or equal to y
< if ( z < 3 ) Is true if z is less than 3
<= if ( z <= y ) Is true if z is less than or equal to y
&& If ( a && b) Is true if both a and b are true
|| If ( a || b) Is true if both a || b are true
! If ( !x ) Is true is x is false
42
Testing Browser Versions<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY><SCRIPT language=JavaScript>if ( navigator.appName == 'Netscape' ) { document.bgColor='#c6c6c6'; document.write( 'name=' + navigator.appName ); document.write( '<br>version=' + navigator.appVersion ); document.write( '<br> appCodename=' + navigator.appCodeName ); document.write( '<br> userAgenet=' + navigator.userAgent );} else { document.bgColor='yellow'; document.write( 'Not netscape name=' + navigator.appName ); document.write( '<br>version=' + navigator.appVersion); document.write( '<br> appCodename=' + navigator.appCodeName ); document.write( '<br> userAgenet=' + navigator.userAgent );}</SCRIPT></BODY></HTML>
When netscape do this
When not netscape do this
43
Summary Introduction to JavaScript
» JavaScript: Its Beginnings– Advantages and disadvantages– How differs from html and server side programs
» Working with JS and HTML tags. » Running onload, when done, on an event» Using JS objects» Objects with properties and methods » Using conditional tests
44
Hands on assignment Write a simple javascript-based web
page that» Redirects the browser to
http://netscape.com if the user is using netscape or firefox
» Redirects the browser to http://microsoft.com otherwise
» Hint: you can redirect a browser by setting the window.location property.
45
One Possible Solution . . .
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY><SCRIPT language=JavaScript>
if ( navigator.appName == 'Netscape') { window.location = 'http://www.netscape.com';} else { window.location = 'http://www.microsoft.com';
}
</SCRIPT></CENTER></BODY></HTML>
46
Another Hands on assignment
Create a webpage with JavaScript that:» Displays the current date » Prompts the user for number of rows, cols
and ticket cost.» Displays number of seats and total
revenue.
47
One Possible Solution
<HTML><HEAD><TITLE>Document Object</TITLE></HEAD><BODY><SCRIPT language=JavaScript>
document.write ("Today is " + new Date().toLocaleString() + "<br>");var rows = parseInt( prompt("How many rows?"));var cols = parseInt( prompt("How many seats per row?"));var ticket = parseInt( prompt("How much per ticket?"));
var size = rows * cols;var rev = size * ticket;document.write( "We have " + size + " total seats.<br>" );document.write( "We have maximum of " + rev + " total revenue.<br>" );
</SCRIPT></CENTER></BODY></HTML>
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