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Client-Side Scripting

Client-Side Scripting . JavaScript. JavaScript. produced by Netscape for use within HTML Web pages. built into all the major modern browsers . properties lightweight , interpreted programming language Integrated with HTML Cross-platform. Usage. T o improve the design

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Client-Side Scripting

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  1. Client-Side Scripting JavaScript

  2. JavaScript • produced by Netscape for use within HTML Web pages. • built into all the major modern browsers. properties • lightweight, interpreted programming language • Integrated with HTML • Cross-platform

  3. Usage • To improve the design • To validate forms • Detect browsers • Create cookies

  4. Syntax <script language = “javascript” type = “text/javascript”> /* Scripts will be written here </script>

  5. Where to use JavaScript

  6. In the <head></head> Syntax: <html> <head><title> JS in head</title> <script language = “javascipt” type = “text/javascript”> </script> </head> <body> <p> body goes here </p> </body> </html>

  7. In the <body></body> Syntax: <html> <head><title> JS in body</title></head> <body> <script language = “javascript” type = “text/javascript”> // scripts here </script> </body> </html>

  8. Along with html elements • Syntax: <html> <head><title>JS along html element </title><head> <body> <button onclick = “JavaScript:alert(‘button’)”> Button Clicked </button> </body> </html>

  9. Linking to external JS Syntax: <html> <head><title>External JS Demo</title> <script language = “JavaScript ” src = “demo.js”> </script> </head> <body> </body> </html>

  10. JavaScript cont.. • Alerting a user • Confirming user’s choice • Prompting a users

  11. Alert • Used to interact with a user by popping up an alert box. • It has an “OK” button by default. • The user should click on the ok button or close the alert box before proceeding.

  12. How alerts work <html> <head><title>Alert box</title> <script language=“JavaScript” type=“text/javascript”> alert(‘Please click ok to continue’); </script> </head>

  13. Confirm Box • To get information back from the user. • Has got “yes” and “no” options.

  14. How confirmation works <html> <head><title>Confirmation Box</title> <script language=“javascript” type=“text/javascript”> confirm(‘can I close this window?’); </script> </head>

  15. Prompt Box • To accept an input from a user. • Has “ok” and “cancel” buttons

  16. How prompt works <html> <head><title>Prompt Box</title> <script language=“javascript” type=“text/javascript”> prompt(‘what is your name:’ , ’enter your name’); </script> </head>

  17. JavaScript cont… • Declaring and using variables • Decisions, loops and functions • Events • Page redirection • Form validation

  18. variables • Can hold any type of data • You can start by storing text and then change to storing numbers without JavaScript having any problems.

  19. How variables work Syntax • Using the keyword var var x; x = 10; alert(x);

  20. Decisions • if • if … else • if … else if … else • switch

  21. if Syntax if (condition) { //executable code; }

  22. if … else Syntax if (condition) { //something here } else { //some other thing }

  23. if … else if … else Syntax if (condition) { //something here } else if (condition) { //some other thing } else { //if both the conditions above are not true execute this }

  24. How they works var x = 5; if (x == 2) { alert(x); } else if(x >5) { alert(‘its five’); } else if(x == 5) { document.write(‘the value of x is: ’ + x); } else { document.write(“no value found”); }

  25. switch Has four (4) statements • Test statement • Case statement • Break statement • Default statement

  26. Switch cont… Syntax switch(test) { case ‘1’: //some code here; break; case ‘2’: // some code here; break; default: //default code }

  27. How switch works var x = “honey”; switch(x) { case “boy”: alert(x); break; case “honey”: alert(“hello ” + x); break; default: alert(“you are not ” + x); }

  28. Loops • Used to iterate while a condition is true • If number of iteration is known use for loop • Otherwise use while loop • To run the code at least one use do…while loop

  29. Loops cont… Loops • for loop • while loop • do … while loop

  30. for loop for ( n= 1; n<= 3; n++) { document.write(n + “<br>”); }

  31. while loop vardegCent= 10; while ( degCent != 100) { document.write(degCent+ “<br>”); degCent+= 10; }

  32. do…while loop • execute at least once, regardless of whether the condition in the while statement evaluates to true. varuserAge; do { userAge= prompt(“Please enter your age: ”,””) } while (isNaN(userAge) == true);

  33. functions • Something that performs a particular task • invoked by: • Event handlers • By statements elsewhere in the script. • Designed for reuse.

  34. functions cont… Syntax: function functionName[arg1,arg2…] { statement[s]; } Remember: function is a keyword and arguments are optional.

  35. How it works <html> <head><title>How to create a function in JavaScript</title> <script language=”javascript” type=”text/javascript”> function displayName(x) { x = prompt(“What is your name please?”,”Enter your name”); alert(“Hello” + x); } </script> </head> <body> <script language=”javascript” type=”text/javascript”> displayName(x); </script> </body> </html>

  36. Events • Used to interact with users • onclick • onmouseover • onmouseout • onLoad • onUnload

  37. How onclick works <body> <script language=”javascript” type=”text/javascript”> function showDate() { document.write(Date()); } </script> <button onclick=”showDate()”>Show Date</button> </body>

  38. How onmouseover works <body> <script language=”javascript” type=”text/javascript”> function displayAlert() { alert(“Your mouse is on the paragraph”); } </script> <p onmouseover=”displayAlert()”>hover your pointer </p> </body>

  39. How onmouseout works <body> <script language=”javascript” type=”text/javascript”> function displayAlert() { alert(“please put your mouse over the paragraph”); } </script> <p onmouseout=”displayAlert()”>hover your pointer </p> </body>

  40. onLoad and onUnload <body onLoad="alert('Hello')" onUnload="alert('Goodbye')">

  41. Page redirection • When you click a URL to reach to a page X but internally you are directed to another page Y that simply happens because of page re-direction. • Why? • Changing your domain name • Search engine already indexed your domain name • Load a specific webpage for a specific browser version

  42. Page redirection cont… • To redirect your site visitors to a new page, you just need to add a line in your head section as follows: <head> <script type="text/javascript"> window.location="http://newlocation"; </script> </head>

  43. Form validation • Used to occur at the server, after the client had entered all necessary data and then pressed the Submit button. • Was lengthy process and over burdening server. • Basic validation • Data format validation

  44. Basic Validation • Make sure data was entered into each form field that required it.

  45. How it works

  46. Data format validation • The data that is entered must be checked for correct form and value

  47. How it works

  48. Document Object Model in JavaScript

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