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COMM 1213 H1 COMP 4923 X1. JavaScript 3 (Readings: Ch. 15 Knuckles). Outline. FOR Loop WHILE Loop Verifying Input using a Loop Sodexo Survey revisited. Repetition via Loops (Ch.15). Sets initial loop index value. The FOR Loop <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript><!--
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COMM 1213 H1COMP 4923 X1 JavaScript 3 (Readings: Ch. 15 Knuckles)
Outline • FOR Loop • WHILE Loop • Verifying Input using a Loop • Sodexo Survey revisited
Repetition via Loops (Ch.15) Sets initial loop index value • The FOR Loop <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript><!-- for (i=1; i<=1000 ; i=i+1) { document.write(i+"<BR>"); } //--></SCRIPT> </HEAD> <BODY> <P> </BODY> </HTML> Sets Boolean condition on which to stop Sets amount to change index on each pass of loop What would happen if the condition i<=1000 was changed to i<=10000000 ?
Using For Loops • Processing the Pizza Toppings Form • Figure 15.4 • Generating random lottery numbers • Figure 15.6
The WHILE Loop • Used when the number of times to loop is not known at the time of writing the code. • Consider the question: Starting from 1, how many numbers must be added until the total exceeds 25,000. • Algorithm: sum = 0 i=1 while sum <= 25000 sum = sum + i i= i+1 • Program – Figure 15.8
Verifying Input <HTML> <HEAD> <SCRIPT LANGUAGE=JavaScript><!-- var pass; pass=prompt("Enter Your Password.",""); correct=false; while(!correct){ if((pass!="buddy")&&(pass!="pal")){ alert("You have entered an incorrect password."); pass=prompt("Enter Your Password. Get it right this time.",""); } else{ correct=true; } } //--></SCRIPT> </HEAD> <BODY BGCOLOR="#FFFFCC"> <P><FONT SIZE="+3"><B>This page contains the darkest secrets of the universe.</B></FONT> </BODY> </HTML> Figure 15.10
Other Fun with LOOPs • Nested Loops and Tables Figure 15.12 • The Sodexo Food survey revisisted • The Sodexo Food survey with a Loop • Uses an array to hold the Food types • The Sodexo Food survey with HTML output
Resources • http://www.w3schools.com/js/js_examples.asp • http://www.tizag.com/javascriptT/index.php • http://www.js-examples.com/page/javascripts.html • http://javascript.internet.com/