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JavaScript: JS301

JavaScript: JS301. Week 2: Advanced Functions, the DOM & jQuery. More on Functions. Functions can be assigned to variables! http://jsfiddle.net/zymsys/REu39/. More on Functions. Functions don’t need names! http://jsfiddle.net/zymsys/B2Yn4/. Variable Scope.

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JavaScript: JS301

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  1. JavaScript: JS301 • Week 2: Advanced Functions, the DOM & jQuery

  2. More on Functions • Functions can be assigned to variables! • http://jsfiddle.net/zymsys/REu39/

  3. More on Functions • Functions don’t need names! • http://jsfiddle.net/zymsys/B2Yn4/

  4. Variable Scope • Up until now our variables have all been global, that that’s BAD!http://jsfiddle.net/zymsys/UnZe8/ • We can solve this by giving our variables local scope:http://jsfiddle.net/zymsys/d2NWX/

  5. Variable Scope • Variables which aren’t defined with ‘var’ are automatically global, which is BAD. • So ALWAYS declare your variables with ‘var’. • Wrapping code in a function is another way to avoid placing anything in the global scope.

  6. Closures • Variables in JavaScript are visible within the closure they are defined in. • Closures are usually functions • http://jsfiddle.net/zymsys/Lu8Kz/

  7. Parameters are References • When you pass a parameter to a function you pass a reference to it, not a copy of it. • http://jsfiddle.net/zymsys/tL9GX/

  8. The Document Object Model (DOM) • The DOM is an object oriented interface which allows JavaScript to interact with web content. • http://jsfiddle.net/zymsys/xef4K/ • http://jsfiddle.net/zymsys/MDTb8/

  9. Working with the DOM is Difficult • In the last example we saw how difficult it can be to do something as simple as tweak an element’s style • There’s a lot of that to deal with, and the cross-browser issues that follow • This is why libraries like jQuery are so popular

  10. jQuery • Here’s the same example with jQuery: • http://jsfiddle.net/zymsys/JmdMM/

  11. Popular Libraries • http://jquery.com/ • http://developer.yahoo.com/yui/ • http://dojotoolkit.org/ • http://mootools.net/ These are just a few of the more popular libraries:

  12. jQuery FTW! • jQuery is very popular: • Easy to find solutions with Google • Lots of plugins and examples • Lots of other libraries already depend on jQuery • jQuery is expressive and relatively easy

  13. jQuery Events • Here’s an update to our jQuery example: • http://jsfiddle.net/zymsys/JmdMM/3/ • No impact on our global namespace!

  14. jQuery Animation • jQuery makes animation easy, just don’t get carried away! • http://jsfiddle.net/zymsys/FaB2f/

  15. jQuery UI • User interface widgets and visual effects • Plenty of demos on the jQuery UI site:http://jqueryui.com/demos/

  16. Next Week • Practical JavaScript • Form Validation • AJAX • Rich User Interfaces • Requests?

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