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This lecture covers essential JavaScript concepts including event handling with onmouseover and onmouseout, arithmetic and logical operators, and control structures like loops. Participants will learn to create interactive web pages through practical examples. The session also includes the creation of a simple calculator, using functions, and displaying system dates. By exploring these foundational elements, students can enhance their web development skills and practical understanding of JavaScript's capabilities in electronic commerce settings.
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CS-3432Electronic Commerce Lecture – 13 SikandarShujahToor https://sites.google.com/site/uolcsecom
onmouseover & onmouseout <HTML> <HEAD><title>Onmouseover event</title></head> <BODY> <IMG SRC=moon.jpg WIDTH=200 HEIGHT=100 BORDER=0 NAME=picture onmouseover="picture.src='moon.jpg';picture.width=500; picture.height=350" onmouseout="picture.src='leopard.jpg';picture.width=600; picture.height=450"> </BODY> </HTML>
Anchor <HTML> <BODY> <A href=leopard.jpg onmouseover="picture.src='moon.jpg';picture.width=500; picture.height=300" onmouseout="picture.src='moon.jpg';picture.width=170; picture.height=50"> <IMG SRC=moon.jpg WIDTH=200 HEIGHT=100 BORDER=2 NAME=picture> </A> </BODY> </HTML>
Operators in JavaScript • + For addition of two numbers and concatenation of two strings • - for subtraction of two numbers • * for multiplication of two numbers • / for division of two numbers • % modulus (calculating the remainder) • ++ increment in number • -- decrement in number
Logical Operators • && logical and • || logical or • ! logical not • if(x<y&&x<z) { any statement } • if(!false){ statement }
Comparison Operators • == Equal • != not equal • < Less than • <= less than equal • > Greater than • >= Greater than equal
Java Script Example <HTML> <HEAD> <TITLE>Javascript Example</TITLE> <SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript"> alert("Thank you for visiting our web site!") </SCRIPT> </HEAD> <BODY> </BODY> </HTML>
Writing on a Page <HTML> <HEAD> <TITLE>example-writing on the page</TITLE> </HEAD> <BODY> <SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript"> <!-- document.write("Hello! Thank you for visiting our site.") //--> </SCRIPT> </BODY> </HTML>
Functions Definition • Function is a block of code which is executed when someone calls it • Defined as follows function my1stfunction(arg1, arg2, arg3) { // some code } • When called, variables and arguments must be in expected order
Displaying System Date <!DOCTYPE html> <html><head><script> function displayDate(){ document.getElementById(“systemdt”).innerHTML=Date(); } </script> </head> <body> <h1>My First JavaScript</h1> <p id=“systemdt">This is a paragraph.</p> <button type="button" onclick="displayDate()">Display Date </button> </body> </html>
Simple Calculator <HTML> <script language="JavaScript"> <!-- function Addit(){ var num1=document.Calform.fst.value; var num2=document.Calform.scnd.value; alert(parseFloat(num1)+parseFloat(num2)); } function minus(){ var num1=document.Calform.fst.value; var num2=document.Calform.scnd.value; alert(parseFloat(num1)-parseFloat(num2)); } //--> </script> <BODY>Add and Subtract Calculator <FORM name="Calform"> <P> 1st Number:<INPUT TYPE="TEXT" NAME="fst" maxlength="3"> <P> 2nd Number:<INPUT TYPE="TEXT" NAME="scnd" maxlength="3"> <P> <INPUT TYPE="button" NAME="Add" VALUE="Add" onclick="Addit()"> <INPUT TYPE="button" NAME="Minus" VALUE="Subtract" onclick="minus()"> <INPUT TYPE="RESET" VALUE="Reset"> </FORM> </BODY></HTML>
Loops • Loops executes a block of code repeatedly until a condition is met • Following types of loops present in JS • For loopfor(intialization;condition;increment){statements} • While loop while(codition){statements} • Do while loop do{statements}while(condition) • Do-while loop executes at least once
For Loop <HTML> <HEAD> <TITLE>Using the For Loop</TITLE> </HEAD> <BODY> <SCRIPT> for(i=1;i<7;i++) document.write("<H"+i+">For Loop Example "+i+“ !! </H“+i+“>"); </SCRIPT> </BODY> </HTML>
While Loop <HTML> <HEAD> <TITLE>Using the While Loop</TITLE> </HEAD> <BODY> <SCRIPT> <!-- var i = 1; while (i < 7){ document.write("<H"+i+">While Loop Example "+i+"!!</H"+i+">"); ++i; } //--> </SCRIPT> </BODY> </HTML>
Do-while Loop <HTML><HEAD> <TITLE>Using the While Loop</TITLE> </HEAD><BODY> <SCRIPT> <!-- var i = 1; do { document.write("<H"+i+">Do-While Loop Example "+i+"!!</H"+i+">"); ++i; } while (i < 1); //--> </SCRIPT></BODY></HTML> • Loop executed once although the condition is false from the beginning
Java Script Objects • Everything in Java Script is an Object which is a combination of data, properties and methods • Properties are the values associated with the object • Methods are the actions which can be performed on the object • New objects can be inherited with “new” key word • person = new Object() • Object Properties can be set / retrieved by using “.” after object name • person.name=“Uzair”; • Methods can be called by the same “.” after object name • var name = persone.getName();
Some Predefined JS Objects • Global • Array • String • Math • Date … etc.
Example of Math object <HTML> <HEAD> <TITLE>Using the Math object</TITLE> </HEAD> <BODY> <H1>Using the Math object </H1> <SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript"> <!-- document.write("Math.PI :" +Math.PI +"<P>"); document.write("Math.LN2 :"+Math.LN2+"<P>"); document.write("Math.sin(90) :"+Math.sin(90)+"<P>"); document.write("Math.random() :"+Math.random()+"<P>"); document.write("Math.pow(2,3) :"+Math.pow(2,3)+"<P>"); document.write("Math.min(123,133): "+Math.min(123,133)+"<P>"); //--> </SCRIPT> </BODY> </HTML>
Array Object <HTML> <HEAD> <TITLE>Using Arrays </TITLE> </HEAD> <BODY> <H1>Using Arrays </H1> <SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript"> <!-- myArray=[0,1,2,3,4,5,6,7,8,9,10]; document.write("myArray: first element " +myArray[0]+"<P>"); document.write("myArray.toString(): "+myArray.toString()+"<P>"); document.write("myArray.join(':'): "+myArray.join(':')+"<P>"); document.write("myArray.reverse(): "+myArray.reverse()+"<P>"); document.write("myArray.sort(): "+myArray.sort()+"<P>"); //--> </SCRIPT> </BODY> </HTML>
