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JavaScript

JavaScript. Chapter 1 - Intro. Why use JavaScript? Interactivity LiveScript JavaScript Jscript ECMAScript JavaScript is not Java! Programming….. . Chapter 2. Do what it says on page 5. The first script. <SCRIPT TYPE="text/javascript" > <!-- alert("Hello world"); //--> </SCRIPT>.

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JavaScript

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  1. JavaScript W. W. Milner

  2. Chapter 1 - Intro • Why use JavaScript? Interactivity • LiveScript JavaScript Jscript ECMAScript • JavaScript is not Java! • Programming….. W. W. Milner

  3. Chapter 2 • Do what it says on page 5 W. W. Milner

  4. The first script <SCRIPT TYPE="text/javascript" > <!-- alert("Hello world"); //--> </SCRIPT> W. W. Milner

  5. Using separate script files <!-- This shows a first piece of JavaScript --> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <title> ----- 1 - HelloWorld ------- </title> <SCRIPT SRC="hithere.js" TYPE="text/javascript"> </head> <body> <p> Some page content </p> </body> </html> W. W. Milner

  6. Chapter 3 • Variables – data values held in memory • Declaring variables • var price=2.50; W. W. Milner

  7. Input Entering data values at ‘run-time’ price = prompt("Enter the price", "10.00"); W. W. Milner

  8. What’s wrong? price = prompt "Enter the price", "10.00"; price = prompt("Enter the price", "10.00"; price = prompt("Enter the price", 10.00); price = prompt( Enter the price", "10.00"); prompt("Enter the price", "10.00"); price = prompt("Enter the price", "10.00") W. W. Milner

  9. Arithmetic • total = price * quantity; • result = 2 + 3; • result = 1 + 3 * 4; • result = (1 + 3) * 4; • result = 7 / 8; • Try page 12 W. W. Milner

  10. Data type • Number, date, currency, boolean… • String type = string of characters • Enclose in quotes – var myName; myName = “Walter Milner”; W. W. Milner

  11. String concatenation • A + joins strings string1 = “fat “; string2 = “cats”; alert(string1+string2); >> fat cats • What is "9" + "9"? W. W. Milner

  12. Changing string type to number • answer = "123.4"; • result = parseFloat(answer); W. W. Milner

  13. Symbol Meaning > greater than < less than >= greater than or equal to <= less than or equal to == equal != not equal if - the decision statement unitPrice = 1.30; if (quantity > 100) unitPrice = 1.20; Do task on page 14 W. W. Milner

  14. Repeating - loops var counter; for (counter=0; counter<4; counter++ ) alert(counter); Do task on page 15 W. W. Milner

  15. Chapter 3 - functions • Code structure - splitting code into parts • Function like mini-program • Data comes in, processed, result returned W. W. Milner

  16. Example function Values come in here function average(a,b,c) { var total; total = a+b+c; return total/3; } Value returned here W. W. Milner

  17. Call and return of function function average(a,b,c) { var total; total = a+b+c; return total/3; } .. x=4; y=3; z=2; answer=average(x,y,z); alert(answer); function call x y z copied to a b c start W. W. Milner

  18. functions do the tasks page 17/18 W. W. Milner

  19. event-handling functions • examples of events - • key press, mouse move, mouse click, timer times out • GUI programming = responding to user events • event-handler = function called when an event happens W. W. Milner

  20. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title> ----- 2 - functions ------- </title> <SCRIPT TYPE="text/javascript" > <!-- function greet() { alert("Loaded"); } //--> </SCRIPT> </head> <body onload="greet()"> </body> </html> The onLoad event do task page 18/19 W. W. Milner

  21. Chapter 5 - The DOM • A way to refer to things in the window • objects • properties • methods • events W. W. Milner

  22. DOM example var newWindow =window.open("","nw", "menubar, status, resizable"); newWindow.status ="Hello folks"; newWindow.resizeTo(400,200); • Do task top of page 21 W. W. Milner

  23. DOM hierarchy window navigator screen document history location form form button form W. W. Milner

  24. navigator • alert(window.navigator.userAgent); the useragent property of the navigator the navigator in the window the window W. W. Milner

  25. screen • readonly window.moveTo(0,0); x = screen.availWidth; y = screen.availHeight; window.resizeTo(x,y ); W. W. Milner

  26. location • location.href="http://www.yahoo.com/"; W. W. Milner

  27. document • document.bgColor="yellow"; • document.write("This is some <b>bold text</b>"); • Try the tasks on page 23 W. W. Milner

  28. Forms • CGI GET and POST and server-side processing • JavaScript client-side processing • Form data validation W. W. Milner

  29. Form example <form name="myform" method="post" action="" > <input type="text" name="num1"> <input type="text" name="num2"> <br> <input type="button" name="Button" value="+" > <br> Result:<input type="text" name="result"> </form> W. W. Milner

  30. Event-handler for button <input type="button" name="Button" value="+" onClick="doAdd()"> function doAdd() { var number1, number2, result; number1=parseFloat(myform.num1.value); number2=parseFloat(myform.num2.value); result = number1+number2; myform.result.value=result; } W. W. Milner

  31. Forms task • Try the task on page 27 W. W. Milner

  32. Form data validation function checkForm() { var OK=true; if (document.form1.forename.value=="") { alert("Please type in your forename"); document.getElementById("fNamePrompt").style.color="red"; OK=false; } if (document.form1.surname.value=="") { alert("Please type in your surname"); document.getElementById("sNamePrompt").style.color="red"; OK=false; } if (OK) { // submit form here } } W. W. Milner

  33. Form validation task • Try the task on page 29 W. W. Milner

  34. Chapter 7 - The Math object function rollDice() { var x = Math.random(); x = 6*x; x = Math.floor(x); x=x+1; alert(x); } Task on page 31 W. W. Milner

  35. Date object var now = new Date(); var result="It is now "+now; document.getElementById("timeField").innerText=result; .. <p id="timeField"> </p> • hours = now.getHours(); • Task on page 32 W. W. Milner

  36. Timing - setTimeout make something happen (once) after a fixed delay interval = setTimeout('bang()', 5000); 5 seconds after this statement executes, this function is called clearInterval(interval); cancels this W. W. Milner

  37. setInterval makes something happen repeatedly at fixed intervals interval = setInterval('ticktock()', 1000); this function is called every second after this clearInterval(interval); stops it W. W. Milner

  38. Timing - tasks • Try page 33 W. W. Milner

  39. Chapter 8 - Standard tricks - rollovers .. function showPic(f) { document.pic.src=f; } // --> </SCRIPT> </head> <body > <p onMouseOver="showPic('pic1.gif')"> Pic one </p> <p onMouseOver="showPic('pic2.gif')"> Pic two</p> <img name = "pic" src="default.gif"> </body> </html> W. W. Milner

  40. Image roll-over <SCRIPT TYPE="text/javascript"> <!-- function showPic(f) { document.pic.src=f; } // --> </SCRIPT>  </head> <body > <img name = "pic" src="default.gif" onMouseOver="showPic('pic1.gif')" onMouseOut="showPic('pic2.gif')" > </body> Task - try this out - produce a page showing an image, which changes to a second image when the mouse goes over it, and a third image when the mouse leaves it. Get images from the Web or draw them using the graphics software on the computer W. W. Milner

  41. Pre-loading images <SCRIPT TYPE="text/javascript"> <!-- var image1, image2, image3; function preLoad() { image1 = new Image(30,30); image2 = new Image(30,30); image3 = new Image(30,30); image1.src="default.gif"; image2.src="pic1.gif"; image3.src="pic2.gif"; document.pic.src = image1.src; } // --> </SCRIPT> </head> <body onLoad="preLoad()" onMouseOver="document.pic.src = image2.src" > <img name = "pic" > </body> </html> W. W. Milner

  42. Menus W. W. Milner

  43. Styles for menus <style type="text/css"> <!-- #ID1, #ID2 { /* initial settings of the two menu blocks */ font-family: Geneva, Arial, Helvetica, san-serif; font-size: 12px; color: #FFFFFF ; display : none; /* <<<< so you cant see them */ background-color= #ffff00; position: absolute; top: 40px; width: 55px; border: thin solid black } .. --> W. W. Milner

  44. JavaScript for the menus function mouseMethod(leftPos, whichID) { /* when they click on a menu item */ /* change from display none to display block - can see it */ document.getElementById(whichID).style.display = "block"; /* make it correct position across screen */ document.getElementById(whichID).style.left = leftPos; } function hideAgain(whichID) { /* when they click hide, revert to display none */ document.getElementById(whichID).style.display = "none"; } Task - Try this out. Add a third block W. W. Milner

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