![JavaScript is Slower than C … … but we can be smarter than matchesSelector! Reprise John Resig’s “The Selectors People Actually Use” From Google Codesearch, for .live() and .delegate() 33% .class 12% tag.class 11% #id 4% tag 4% tag[attr=value] 68% match tag#id.class[attr=value]](https://image.slidesharecdn.com/jquery17eventswork-111002124951-phpapp01/85/jQuery-1-7-Events-20-320.jpg)
jQuery 1.7 Events
- 2. 1.7 Event Goals: Simplify the API
- 3. 1.7 Event Goals: Make It Faster!
- 4. 1.7 Event Goals: Reduce Overall Size
- 5. 1.7 Event Goals: Fix Existing Bugs
- 6. 1.7 Event Goals: Don’t Break It
- 8. .on() and .off() Unifies bound and delegated events $().on(events, “selector”, data, handler); $().off(events, “selector”, handler); Maps straightforwardly to old APIs: $(“a”).bind(“click change”, { mydata: 42 }, fn); $(“a”).on(“click change”, { mydata: 42 }, fn); $(“.box”).delegate(“a”, “click.myplugin”, fn); $(“.box”).on(“click.myplugin”, “a”, fn); $(“a”).live(“click”, fn); $(document).on(“click”, “a”, fn);
- 9. Benefits Ends confusion about interaction across event APIs $( “a” ). live ( “click” , function(){ alert( “Hello” ); }); $(document). unbind ( “click” ); // live is now dead! $(document). on ( “click” , “a” , function(){ alert( “Hello” ); }); $(document). off ( “click” ); Consistent pronunciation (unlike live/die ) Chainable with traversal/filter methods (unlike live ) Argument order is consistent (unlike delegate ) Shorter to type ( off vs. undelegate ) No confusion with ES5 Function.bind Saved 1,122 bytes removing bind/live/delegate in 1.7
- 11. Yes: bind, live, delegate work in 1.7!
- 12. No need to panic
- 13. Event Delegation is Great, But … W3C sez: Determine handlers before delivery A handler can’t change which subsequent handlers are called, other than .stopPropagation() and .stopImmediatePropagation() jQuery must selector-match up to the delegation point Protip: D elegate to the nearest possible element
- 14. Don’t Make Me Bubble, Bro! (document) $(“.submenu-item”).live(“click”, myFn ) <html> <body class=“js”> <div id=“wrapper”> <ul id=“nav”> $(“#nav”).on(“click”, “.submenu-item”, myFn ) <li class=“flyout”> Text size <ul class=“submenu”> <li class=“submenu-item”>Medium</li> Browser bubbles to the delegation point, calls the jQuery handler jQuery selector-matches, again bubbling to the delegation point jQuery runs the user’s handler(s) (in this case, myFn)
- 15. No Pressure, But …
- 17. Test Case Profile in 1.6.3: 15.1 secs
- 18. Test Case Profile in 1.7: 5.6 secs
- 19. Therefore …
- 20. JavaScript is Slower than C … … but we can be smarter than matchesSelector! Reprise John Resig’s “The Selectors People Actually Use” From Google Codesearch, for .live() and .delegate() 33% .class 12% tag.class 11% #id 4% tag 4% tag[attr=value] 68% match tag#id.class[attr=value]
- 21. A Plan Materializes: quickIs() Attempt to pre-parse the selector during event attach If it matches the subset, save the parsed components At event delivery, selector check is just one statement Complex selectors work, they just take the Sizzle path (Show the codez)
- 23. How Fast Is It Now? Delegated event delivery time (milliseconds): Let us not speak of event overhead again. Browser jQuery 1.6.3 jQuery 1.7 Beta Chrome 13 3.0 1.1 (2.8x) Firefox 6 4.0 1.5 (2.7x) IE 7 55.6 13.1 (4.2x) IE 9 9.6 2.3 (4.1x) IE10 PP 8.2 2.1 (3.9x)
- 25. Make Events More Hookable Existing code had some hard-wired special cases: mouseenter/mouseleave on delegated events Delegated events put under a “live” event – not DRY New special event hooks simplified code: trigger hook called from jQuery.event.trigger() handle hook called from jQuery.event.handle() New event property hooks (propHooks) Fixes up event object when a native event occurs Allows code to run only for specific events Copies only relevant event properties Example: Normalize event.pageX/pageY for mouse events
- 26. Internet Explorer Can’t Be Forgotten
- 27. Change/Submit for IE 6, 7, 8 A must-have for useful event delegation jQuery special event hooks for old IE, since 1.4 Fake bubbling submit event by listening for click/keypress Fake bubbling change event by listening for lots o’ stuff Unfortunately, fake isn’t always good enough Events don’t fire in expected order Complex special cases that require lots of code to fix Heroic failed effort, so let’s try Plan B: Listen for the earliest possible event on an element Attach a real submit/change event and bubble it manually jQuery cleanup takes care of removing the event
- 28. Event Bugs Fixed in 1.7 Many fixed in the course of overall code restructure Oldest bug was from February 2010 Open Bugs Open Feature Requests jQuery 1.6.4 28 4 jQuery 1.7 beta 3 1
- 29. In Summary …
- 30. It Passes Unit Tests, But …
- 31. We Need Your Help Testing
- 32. It Do All Things! What You Think? Google+, email: dave.methvin@gmail.com Twitter: @davemethvin Github: dmethvin
- 33. And now … OM NOM NOM!