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Wednesday

Wednesday. Homework 1 = due by email by 4pm Submit to gillw3@rpi.edu (zip your files). Apps v. web apps. Discuss…. JS. Javascript. Javascript. Client Side Scripting Language Object Oriented Event Driven. Places JS Lives. An External File <head> of an HTML file

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Wednesday

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  1. Wednesday • Homework 1 = due by email by 4pm • Submit to gillw3@rpi.edu (zip your files)

  2. Apps v. web apps • Discuss….

  3. JS Javascript

  4. Javascript • Client Side Scripting Language • Object Oriented • Event Driven

  5. Places JS Lives • An External File • <head> of an HTML file • In the <body> of an HTML page • (after all the elements it may reference) • JS can be used in multiple locations in the same HTML document

  6. A link to an external javascript document A JS Script coded in the <head> of an HTML document

  7. External JS Files Don’t put another set of <script> tags inside your external JS docs

  8. JS Inside HTML

  9. Variables • All are untyped • Local Variables • Accessible only inside the current function • Global by assignment

  10. Literals

  11. Operators

  12. Control Structure • If • If / else • Switch • For • While • For (object)

  13. IF • If • If / Else

  14. Switch

  15. Loops • For • While

  16. Looping over an Object

  17. Functions • Declaring a Function • Calling a Function

  18. Events http://www.w3schools.com/jsref/jsref_events.asp

  19. Timer Events • Run JS in the future • setTimeout(“js code”, milliseconds); • Code must be in quotes!!!!!!!!! • setTimeout(“print_time()”,1000);

  20. Timer Events • Do every N seconds: Function do(){ ….. Code; setTimeout(“do()”,1000); }

  21. Events

  22. JS Objects • Properties • A value held by an object • Methods • Act upon an object A string property A string method

  23. String Methods • str.substr(start, length) • Returns a sub string • str.indexOf(seach) • Returns position of the first instance of search • str.replace(bad, good) • Replaces bad text with good text • str.split(delimiter) • Breaks string into an array at every instance of delimiter

  24. String Properties • str.len • Returns length of a string

  25. Math Methods • Math.ceil(x) • Rounds up to the next integer value • Max(x,y) • Picks the larger of the two arguments • Math.random() • Returns a random number between 0.0 and 1.0

  26. Document Object • Properties • Document.URL • Returns current url and query string • Methods • document.writeln() • Prints a line in the current document • Document.getElementById(id) • returns an HTML element with the ID you provide

  27. Debugging • Web dev tool bar: • Click the red exclamation marks to see errors • alert(somevar); • alert(‘working at line 36’);

  28. In Class • Write a ‘hello world’ script put it inside the body of an HTML document • View the generated html … what’s happened here? • Write a ‘hello world’ function – call it on body onload • View the generated html … what’s happened here?

  29. In Class • Write a script that generates the following text: 1+1, 1+2, …., 1+10 • If the user clicks on one of these items, produce an alert box with 1+1 = 2 (for example)

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