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AngularJS - Overcoming performance issues. Limits.

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Presented as speaker at CodeCamp (Iasi - 2014).

Presented as speaker at CodeCamp (Iasi - 2014).

Published in: Software, Technology, Business

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  • 1. AngularJS. Performance & Limits. Dragos Rusu - CodeCamp Iasi 2014 (dragos.rusu@bytex.ro)
  • 2. Our story From "We have to rethink this whole module, remove time navigation... it's just too sluggish." ★ to "It's awesome, really fast, it's like going from night to day!" ★ (★) SOFTVISION customer
  • 3. A few words about me Dragos Rusu @ SOFTVISION WEB/ZEND ENGINEER since 2007 (backend, frontend) ARTICLE WRITER (PHP Architect) PROJECTS: platforms for airlines (Cathay Pacific, Singapore Airlines, Air Berlin), tourism agencies, home automation and security, agriculture
  • 4. We will discuss about... 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits Q / A
  • 5. disclaimer PERFORMANCE principles for heavy apps (+500 man days) * many items are not covered here. * code samples - only in AngularJS never used AngularJS before? no problem, principles are general, yet the solutions are particular.
  • 6. Shall we?
  • 7. 1. View watches / data bindings
  • 8. GENERAL CONTEXT "more of 2000 watchers can lag the UI" (angular-tips.com) "the expressions in curly braces denote bindings" ({{ ... }}) (docs.angularjs.org) "AngularJS internally creates a $watch for each ng-* directive" (github.com/Pasvaz/bindonce) "ngRepeat directive instantiates a template once per item [...] each template instance gets its own scope" (docs.angularjs.org)
  • 9. Ok... but why would I be counting watches?
  • 10. Every watcher is run at the digest cycle. The digest cycle is repeated until none of the results has changed value (Brian Ford - AngularJS contributor)
  • 11. ✈ A peak into AngularJS source code $apply:function(expr){ try{ beginPhase('$apply'); returnthis.$eval(expr); }catch(e){$exceptionHandler(e); }finally{ clearPhase(); try{ $rootScope.$digest();//Ouhmy... //[...] ? https://github.com/angular/angular.js/blob/ master/src/ng/rootScope.js#L943
  • 12. (1) double-binding creates tons of listeners
  • 13. SOLUTION: Whenever feasible, use single-binding solutions double binding DEMO / bindonce DEMO
  • 14. Why? Is double-binding slow? Not quite. The AngularJS way of implementing it is slow ($dirty flags instead of observable properties). pssst: ECMA6: Object.observe()
  • 15. github.com/Pasvaz/bindonce github.com/kseamon/fast-bind pssst: bindonce will be part of AngularJS 1.3 release!
  • 16. (2) direct function calls from templates are called very often SOLUTION: pre-compute the values to shown in the view model (default values, totals, etc) <ul> <ling-repeat="iteminitems"> //{{item.name}}({{computeTotal(item)}}) {{item.name}}({{item.computedTotal}}) </li> </ul> ?
  • 17. EXAMPLE vatTotal will be recomputed on each scope $digest, regardless if the values that vatTotal() depend on are changed or not (DEMO) //...controller... $scope.vat=24;//% $scope.vatTotal=function(){ return( $scope.data.item.total* (1+$scope.vat/100) ); }; //...template... {{vatTotal()}} ?
  • 18. (3) iterating over large data sets slows down the page SOLUTION: create a lightweight iterable view model angular.module('codecamp').controller('testCtrl',[ '$scope','dm','$q',function($scope,dm,$q){ 'usestrict'; $scope._init=function(){ $scope.testViewModel={}; $q.all([dm.getData1(),dm.getData2()]) .then(function(response){ $scope.computeViewModel(response.data); } ); }; $scope._init(); } ); ?
  • 19. (4) ng-repeat extra DOM manipulations SOLUTION: ng-repeat with track by id (DEMO) <ul> <ling-repeat="iteminitemstrackbyitem.id"> {{item.name}} </li> </ul> ?
  • 20. (5) filters are called very often SOLUTION: lightweight quasi-independent filters <span>{{value}}</span> <ul> <ling-repeat="iteminitems"> {{item.name|heavyFilteritem.value,$index}} </li> </ul> ? WARNING: avoid touching DOM in filters and watches
  • 21. (6) multiple recursive $watch might cause page flickering SOLUTION: try to avoid recursive watch, where feasible $scope.$watch('model.items', function(newValue,oldValue){ //dosmth },recursive=true); ); ?
  • 22. (7) direct DOM watch functions might slow down the page SOLUTION: try to avoid complex valueExpression, where feasible (use the data model instead) //DirectiveLINKfunction link:function($scope,$el,$attrs){ $scope.$watch( function(){return$el[0].childNodes.length;}, function(newValue,oldValue){} ); } ? SOURCE: stackoverflow.com/questions/21332671
  • 23. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 24. 2. What you see is what you show
  • 25. ng-if vs. ng-show (1) ng-hide and ng-show makes no speed difference (DEMO) <ulng-hide="hideCondition"> <ling-repeat="iteminitems"> {{item.value}} </li> </ul> ?
  • 26. ng-if vs. ng-show (2) ng-if/ng-switch might make a difference on more content (e.g. tabbed page) <ulng-if="displayCondition"> //CONTENT </ul> ? * fewer bindings * fewer linkers called at startup
  • 27. remove non-visible elements in the scroll (1) one easy way would be PAGINATION doesn't always apply though...
  • 28. remove non-visible elements in the scroll (2) DISPLAY elements, but ONLY THE VISIBLE ones known as the VIRTUAL/INFINITE SCROLLING problem
  • 29. remove non-visible elements in the scroll (3) usually occurs when large data sets need to be displayed OpenSource solutions: http://binarymuse.github.io/ngInfiniteScroll/ http://blog.stackfull.com/2013/02/AngularJS-virtual-scrolling-part-1/ DEMO / DEMO (with virtual scroll)
  • 30. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 31. 3. The risk of polluting scopes
  • 32. ✈ DOM / SCOPES
  • 33. (1) relying on multiple $rootScope and appCtrl functions may slow down the $digest SOLUTION: try to avoid polluting $rootScope/appCtrl/* scopes angular.module('codecamp').service('appInit',[ '$rootScope',function($rootScope){ 'usestrict'; $rootScope.computeStuff=function(){...}; $rootScope.getData=function(){...}; $rootScope.i18n=function(){...}; $rootScope.manageAppStates=function(){...}; $rootScope.manageFormatters=function(){...}; //...andsoforth }); ? - dispatch to specialized services/factories/filters/*
  • 34. ... and have some privacy in all scopes angular.module('codecamp').controller('testCtrl',[ '$scope',function($scope){ 'usestrict'; $scope._privateMethod=function(){}; functionnotRecommended(){ //... } }); ?
  • 35. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 36. 4. Core directives to avoid
  • 37. ALL of them ... right
  • 38. Remember what we've said earlier? "more of 2000 watchers can lag the UI" (angular-tips.com)
  • 39. varngEventDirectives={};forEach( 'clickdblclickmousedownmouseupmouseoverblur mouseoutmousemovemouseentermouseleavecopy keydownkeyupkeypresssubmitfocuscutpaste' .split(''),function(name){//[...] returnfunction(scope,element,attr){//LINK element.on(lowercase(name),function(event){ //scope.$apply=>$rootScope.$apply scope.$apply(function(){ fn(scope,{$event:event}); }); //[...] ? SOURCE: github.com/angular/angular.js/blob/ master/src/ng/directive/ngEventDirs.js#L41
  • 40. Does that really matter? video not displayable Quad core, 8 GB of RAM, Win7
  • 41. Seems so... video not displayable
  • 42. SOLUTION: write custom directive(s), catch the events you need and... .directive('customMouseEnter',[ function(){ 'usestrict'; return{ restrict:'A', link:function(scope,elem,attrs){ varfName=attrs.customMouseEnter, func=function(ev){ scope[fName](ev); }; elem.on('mouseenter',func); scope.$on('$destroy',function(){ elem.off('mouseenter',func); }); //[...] ?
  • 43. ...trigger local $digests (DEMO $digest over $apply) //TEMPLATE <trcustom-mouse-enter="ctrlMouseLeave"> //CONTROLLER/DIRECTIVE scope.mouseLeave=function(ev){ //highlight,etc //$digest()onlyonthescopeyouneed scope.$digest(); }; ?
  • 44. Seems to be pretty common in the community http://stackoverflow.com/questions/18421732/angularjs-how-to-override-directive-ngclick http://briantford.com/blog/angular-hacking-core (★) if you actually override default directives, remember to set a higher priority
  • 45. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 46. 5. Splitting the page
  • 47. identify what is shareable and what is not avoid splitting the page in too many sub-components design your components in a blackbox manner
  • 48. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 49. 6. Miscenallaneous
  • 50. (1) evalAsync(f) over $timeout(f) More: http://www.bennadel.com/blog/2605-scope-evalasync-vs-timeout-in-angularjs.htm
  • 51. (2) Watch out for external components performance and their usage We had a problem with Moment.JS library (20% of the page load time, according to Chrome Profiler)
  • 52. (3) $eval your code from time to time - PERF wise Batarang (identify $watchers), Chrome Profiler (memory, performance), performance.now()
  • 53. (BONUS) demythify events
  • 54. $emit / $broadcast (1) SOURCE: jsperf.com/rootscope-emit-vs-rootscope-broadcast/24
  • 55. $emit / $broadcast (2) SOURCE: jsperf.com/rootscope-emit-vs-rootscope-broadcast/25
  • 56. Ok... but why? AngularJS 1.2.6 and below ▶ 12-15x difference AngularJS 1.2.7+ ▶ 1.1x difference "limit propagation of $broadcast to scopes that have listeners for the event" (github.com/angular/angular.js/blob/master/CHANGELOG.md#performance-improvements-3) RECAP: Common sense still says we should use them according to their design
  • 57. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 58. 7. Limits
  • 59. "you quickly reach the end of what Angular can do for you when it comes to structuring applications, at which point the community fragments transform to best practices, and few people have figured out how to write large-scale Angular apps" (EmberJS core member)
  • 60. Technical limits 1. + 2.000 dynamic elements on the screen 2. + 3.000 watchers 3. real time apps, where data changes very often (★) depending on the device
  • 61. Some apps examples: stocks exchange google maps office apps OUTPUT: screen flickering, low UX, unresponsive screens And there's nothing you can do about it... except rewriting it in a lightweight framework
  • 62. 1. View watches / data bindings 2. What you see is what you show 3. The risk of polluting scopes 4. Core directives to avoid 5. Splitting the page 6. Miscellaneous 7. Limits
  • 63. Recap? (1) (1) be aware of too many data bindings (bindonce) (2) try to minimize the number of $digest cycles (3) have pre-computed values at template level (4) display only the visible elements (virtual scroll)
  • 64. Recap? (2) (5) be aware of core directives PERF problems (6) don't pollute your scopes and make them TDD friendly (7) watch out for external components (angular or non-angular) performance
  • 65. What's next? it's a good habit to think PERF (pre-$compile the code in your head) don't assume the frameworks are fast, whatever you may write watch out for memory leaks REMINDER: AngularJS is quite easy, just try it! ... and last but not least important: find a company that would allow you to grow your skills!
  • 66. Q / A