Performance-driven front-end development


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Performance-driven front-end development

  1. 1. Performance-driven front-end development 2013-10-25 By Zhang Hongliang Online slide show Raxtone
  2. 2. Concepts • • • • Layout is the process by which Chrome calculates the positions and sizes of all the elements on the page. Reflow (aka layout thrashing )is the name of the web browser process for re-calculating the positions and geometries of elements in the document, for the purpose of re-rendering part or all of the document. A repaint occurs when changes are made to an elements skin that changes visibility, but do not affect its layout. A web browser engine, (sometimes called layout engine or rendering engine), is a software component that takes marked up content (such as HTML, XML, image files, etc.) and formatting information (such as CSS, XSL, etc.) and displays the formatted content on the screen. – Main engine Raxtone
  3. 3. Raxtone
  4. 4. Main engine Raxtone
  5. 5. Sources • Tools – Canary or chrome • Open a Chrome window in incognito mode(ctrl+shift+n) – Devtools – Pagespeed insights • Links( slash not omitted ) – – – Raxtone
  6. 6. Problems Performance Tooling by Paul Irish (#perfmatters at SFHTML5) YouTube Raxtone slide
  7. 7. Page load • The DOMContentLoaded event is fired when the document has been completely loaded and parsed, without waiting for stylesheets, images, and subframes to finish loading (the load event can be used to detect a fully-loaded page). • The load event is fired when a resource and its dependent resources have finished loading. Raxtone
  8. 8. External cause Region Platform Network GTmetrix Raxtone
  9. 9. User perception Raxtone
  10. 10. Ideal situation Raxtone
  11. 11. Current situation • The study found that the median load time for first-time visitors to a retail website’s home page was 7.25 seconds • 57% of online shoppers will wait 3 seconds or less before abandoning the site. • based the 3 seconds ideal load time on pc (source:PhoCusWright/Akamai report) Raxtone
  12. 12. Page load time Chrome(Canary): Devtools – Network (open Devtools and refresh) Raxtone
  13. 13. Network waterfall • resources in the Network table are sorted by the start time of each request (the network "waterfall"). – the request's latency and receipt time are displayed above the corresponding bar's light- and dark-shaded areas, respectively Raxtone
  14. 14. Solution - methods Sprite,combine •Missing Trailing Slash •Connecting Web Sites Including css,html Common module $.ajax cache default Raxtone
  15. 15. Solution - tool • Use PageSpeed Insights to identify performance best practices that can be applied to your site, and PageSpeed optimization tools to automate the process of applying those best practices. Raxtone
  16. 16. PageSpeed Insights • Best Practice(help page) S sprite Raxtone
  17. 17. PageSpeed Insights • Before building Grunt tasks: Concat Cssmin uglify htmlmin imagemin Raxtone
  18. 18. PageSpeed Insights • After building (suggestion config by server client) Raxtone
  19. 19. Image assets • Pc portal Raxtone
  20. 20. Solution • grunt-contrib-imagemin – Minify PNG and JPEG images Raxtone
  21. 21. Non-blocking delivery • Limiting yourself to downloading a single large JavaScript file will only result in locking the browser out for a long period of time, despite it being just one HTTP request. Raxtone
  22. 22. Solution • The secret to nonblocking scripts is to load the JavaScript source code after the page has finished loading. – – – – – Asynchronous Script Positioning Deferred Scripts Requirejs Jquery.lazyload Raxtone
  23. 23. Critical path css • External CSS stylesheets are renderblocking, meaning the browser won’t paint content to the screen until all of your CSS – specifically, media=’screen’ CSS – arrives. – Source: Detecting Critical CSS For Above-the-Fold Content Raxtone
  24. 24. Solution • Prioritize visible content – one (and only one) external CSS file – an inlined CSS block that is page specific and allows your above the fold content to load immediately. Raxtone
  25. 25. @font-face load • 1) custom fonts are awesome and we want to use them • 2) custom fonts slow down our pages by being large additional resources. Raxtone
  26. 26. Solution • Only load on large screens • Ajax in the fonts • Lazy load the fonts, load on subsequent page loads after cached – Source: Preventing the Performance Hit from Custom Fonts Raxtone
  27. 27. Runtime • Run time (program lifecycle phase) – In computer science, run time, run-time, runtime, or execution time is the time during which a program is running (executing), in contrast to other phases of a program's lifecycle such as compile time, link time, load time, etc. Raxtone
  28. 28. Interation • Human–computer interaction – Human–computer interaction (HCI) involves the study, planning, and design of the interaction between people (users) and computers. Raxtone
  29. 29. Transitions & animations • The CSS transition property is a shorthand property for transition-property, transition-duration, transition-timingfunction, and transition-delay. It allows to define the transition between two states of an element. Different states may be defined using pseudo-classes like :hover or :active or dynamically set using JavaScript. • The animation CSS property is a shorthand property for animation-name, animation-duration, animation-timingfunction, animation-delay, animation-iteration-count and animation-direction. Raxtone
  30. 30. Solution Raxtone
  31. 31. Example 1 - 1 • Source: flynavi project • Tool: devtools - Raxtone
  32. 32. Example 1 - 2 Show composited layer borders: It can indicate the rendered elements which may be animating or have CSS transforms/ transitions applied to them that change the shape or positioning of the element. Raxtone
  33. 33. Example 1 - 3 • Applying transform style Raxtone
  34. 34. Example 1 - 4 • Enable continuous page repainting – This is a tool that helps you identify elements on the page which are costly. The page will continuously repaint, showing a counter of how much painting work is happening. – Paint hurts on low-end devices Raxtone
  35. 35. Example 1 - 5 Raxtone
  36. 36. Scrolling • Scrolling areas are used to let the user move text and/or images across the device's display. Raxtone
  37. 37. Memory leak & GC • • • A memory leak is a gradual loss of available computer memory. It occurs when a program repeatedly fails to return memory it has obtained for temporary use. JavaScript web apps can often suffer from similar memory related issues that native applications do, such as leaks and bloat but they also have to deal with garbage collection pauses. In computer science, garbage collection (GC) is a form of automatic memory management. The garbage collector, or just collector, attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program. Problem: – Is my page using too much memory? – Is my page free of memory leaks? – How frequently is my page forcing garbage collection? Raxtone
  38. 38. Key point - layout thrashing • Outside of initial page load problems, “layout thrashing” is the most common performance problem in dynamic web applications. This is particularly true for Single Page Applications which build and destroy views on the fly. Raxtone
  39. 39. Solution - Minimize reflow • Reduce unnecessary DOM depth. Changes at one level in the DOM tree can cause changes at every level of the tree all the way up to the root, and all the way down into the children of the modified node. • Minimize CSS rules, and remove unused CSS rules. • If you make complex rendering changes such as animations, do so out of the flow. Use position-absolute or position-fixed to accomplish this. • Avoid unnecessary complex CSS selectors - descendant selectors in particular - which require more CPU power to do selector matching. Raxtone
  40. 40. What causes the browser to layout? innerHTML Raxtone
  41. 41. RequestAnimationFrame • The window.requestAnimationFrame() method tells the browser that you wish to perform an animation and requests that the browser call a specified function to update an animation before the next repaint. The method takes as an argument a callback to be invoked before the repaint. Raxtone
  42. 42. The basic tools • The workbench becomes the center of the wood shop, the craftsman returning to it time and time again as a piece takes shape. -- The pragmatic programmer by Andrew Hunt David Thomas Raxtone
  43. 43. Devtools • Devtools – Timeline Raxtone
  44. 44. Libraries • FastDom – Target » Eliminates layout thrashing by batching DOM read/write operations – Principle » Each read/write job is added to a corresponding read/write queue. The queues are emptied (reads, then writes) at the turn of the next frame using window.requestAnimationFrame. Raxtone
  45. 45. Example 1 • The code shared on jsfiddle. – Move a div element Raxtone
  46. 46. Example 2 • Positioning button animation(flynavi project) Raxtone var position_interval = null; void function () { var num = 0 ,interval=200, preFrameTime=0 position_interval = requestAnimationFrame(function (stampTime) { var duration = stampTime - preFrameTime; if(duration< interval){ requestAnimationFrame(arguments.callee) return } /* 填加自车位置后,隐藏正在定位按钮样式 */ if (mapHandler.mapObj && mapHandler.curMarker) { positionStateEnd(); return; } preFrameTime=stampTime …
  47. 47. Example 3 - 1 • 3,innerText leading to layout Raxtone
  48. 48. Example 3 - 2 • Before modified $('#normal_withTime_one').text(util_common.formatMinute(Math.round(newVal.timeExtend10/60))); $('#normal_withTime_two').text(util_common.formatMinute(Math.round(newVal.timeExtend20/60))); After modified fastdom.write(function () { $('#normal_withTime_one').text(util_common.formatMinute(Math.round(newVal.timeExtend10 / 60))); $('#normal_withTime_two').text(util_common.formatMinute(Math.round(newVal.timeExtend20 / 60))); }) Raxtone
  49. 49. Example 4 • Comprehensive use: coffeescript, requirejs, fastdom, javascriptmvc, RWD, refactor define(['fastdom','jquerymx'] ,(fastdom)-> $.Model('MapRouteView', { setUi: -> $path_info = $('#path_info')> top1 = $path_info.position().top - 57 top2 = $path_info.position().top - 94 fastdom.write(-> $('#zoom_out').css('top', top1); $('#zoom_in').css('top', top2); $('#tmc_btn').hide(); $('#navi').hide("fast", -> $path_info.css({'visibility': 'visible'}) ) ) ) } ) ) Raxtone require(['mapRouteView'],function(){ setMapRouteView = new MapRouteView(config); setMapRouteView.displayData(); })
  50. 50. Qualification Raxtone
  51. 51. Todo • Turn on pain rects, layer borders, continuous repainting • about:tracing • bootstrap • Css lib – Topcoat • Tool – speed curve – WebPageTest Raxtone
  52. 52. Thanks • • • • • @twitter @paul_irish @ChromiumDev @YouTube Other internet resources Raxtone
  53. 53. Raxtone