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Angular Performance: Then, Now and the Future

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AngularJS the performance parts @toddmotto


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» Lead Engineer @ Mozio » Google Developer Expert » @toddmotto » Blog at toddmotto.com


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Topics » New features (1.2 - 1.3+) » Generic changes » Perf features » Performance driven Angular » $digest loop/$$watchers/$$asyncQueue » Quick wins, tips and tricks » Structure practices, advanced techniques


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1.2 to 1.3+


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1.2 to 1.3+ generic changes


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» IE8 support dropped » DOM manipulation » ~4.3 times faster » 73% less garbage » $digest loop » ~3.5 times faster » 78% less garbage » 400+ bug fixes


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1.2 to 1.3+ perf features


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» One-time bind syntax » ngModelOptions » bindToController property » ngModel.$validators » ngMessage/ngMessages » strictDI » $applyAsync in $http » Disable debug info


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one time bindings <p>{{ ::vm.name }}</p> <p ng-bind="::vm.name"></p> <div ng-if="::vm.user.loggedIn"></div> <div ng-class="::{ loggedIn: vm.user.loggedIn }"></div> <ul> <li ng-repeat="user in ::vm.users"> {{ ::user.name }} </li> </ul>


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one time bindings » Defined with :: » $watched until not "undefined" » $$watcher is unbound » Will not update upon Model changes » One-time, not one-way » Great for single static rendering


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ng-Model-Options <!-- updateOn --> <input type="text" ng-model="vm.model" ng-model-options="{ updateOn: 'default blur' }">


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ng-Model-Options <!-debounce: - example will debounce 250ms when typing - example will update model immediately on "blur" --> <input type="text" ng-model="vm.model" ng-model-options="{ updateOn: 'default blur', debounce: { 'default': 250, 'blur': 0 } }">


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ng-Model-Options // directive controller function FooDirCtrl() { // undo model changes if (condition) { this.model.$rollbackViewValue(); } }


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ng-Model-Options » Fine tune how Model updates are done » Define event types » Add debounce to delay Model synchronisation » e.g. { debounce: 250 } = $digest ~250ms » $rollbackViewValue for undoing model changes


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bindToController // directive controller function FooDirCtrl() { this.bar = {}; this.doSomething = function doSomething(arg) { this.bar.foobar = arg; }.bind(this); }


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bindToController // directive controller function FooDirCtrl($scope) { this.bar = {}; this.doSomething = function doSomething(arg) { this.bar.foobar = arg; // reference the isolate property $scope.name = arg.prop; }.bind(this); }


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bindToController function fooDirective() { return { ... scope: {}, bindToController: { name: '=' }, ... }; }


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bindToController // directive controller function FooDirCtrl() { this.bar = {}; this.doSomething = function doSomething(arg) { this.bar.foobar = arg; // reference the isolate property this.name = arg.prop; }.bind(this); }


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bindToController » Used with "controllerAs" (class-like) » Binds isolate props to the Controller instance » No $scope » $scope remains "special use only" » Not used for data » Used for $watch/$on/etc


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ngModel.$validators // old school function visaValidator() { var VISA_REGEXP = /^4[0-9]{12}(?:[0-9]{3})?$/; function link($scope, element, attrs, ngModel) { ngModel.$parsers.unshift(function (value) { var valid = VISA_REGEXP.test(value); ngModel.$setValidity('visaValidator', valid); return valid ? value : undefined; }); } return { require : 'ngModel', link : link }; } angular.module('app').directive('visaValidator', visaValidator);


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ngModel.$validators // new school function visaValidator() { var VISA_REGEXP = /^4[0-9]{12}(?:[0-9]{3})?$/; function link($scope, element, attrs, ngModel) { ngModel.$validators.visaValidator = function (value) { return VISA_REGEXP.test(value); // Boolean }; } return { require : 'ngModel', link : link }; } angular.module('app').directive('visaValidator', visaValidator);


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ngModel.$validators <form name="myForm"> <label> <input type="text" ng-model="myForm.card" visa-validator> <div ng-if="myForm.myPassword.$error.visaValidator"> Not a valid VISA format! </div> </label> </form>


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ngModel.$validators » ngModel.$validators Object » Instead of $parsers/$formatters » Return a Boolean from the bound function » Use with the $error Object in the View


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ngMessage/ngMessages <form name="myForm"> <label> Enter email: <input type="text" ng-model="field" name="myField" required ng-minlength="5" ng-maxlength="100"> </label> <div ng-messages="myForm.myField.$error" role="alert"> <div ng-message="required"> You did not enter a field </div> <div ng-message="minlength, maxlength"> Your email must be between 5 and 100 characters long </div> </div> </form>


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ngMessage/ngMessages » Conditional validation » ngModel.$error Object » Acts like a switch case


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strictDI <div ng-app="myApp" ng-strict-di> <!-- app --> </div>


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strictDI // implicit annotation function SomeService($scope, $timeout) { //... } angular .module('app') .factory('SomeService', SomeService);


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strictDI function SomeService($scope, $timeout) { //... } // Array annotations SomeService.$inject = ['$scope', '$timeout']; angular .module('app') .factory('SomeService', SomeService);


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strictDI » Runs the application's $injector in strict mode » Throws an error on Services using implicit annotations » Use ng-annotate to automate this process


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$applyAsync with $http function config($httpProvider) { $httpProvider.useApplyAsync(true); } angular .module('app', []) .config(config); More: blog.thoughtram.io/angularjs/2015/01/14/exploring-angular-1.3-speed-up-with-applyAsync.html


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$applyAsync with $http » Enables $applyAsync to be used with $http » Schedules an async $apply for batched requests » For requests that resolve within ~10ms » Pushes into $$asyncQueue » Single $digest


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Disable debug info function config($compileProvider) { $compileProvider.debugInfoEnabled(false); } angular .module('app', []) .config(config);


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Disable debug info <!-- enabled --> <div ng-controller="MainCtrl as vm" class="ng-scope ng-binding"> <my-directive class="ng-isolate-scope"> // content </my-directive> </div> <!-- disabled --> <div ng-controller="MainCtrl as vm"> <my-directive> // content </my-directive> </div>


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Disable debug info » Disable in production for performance boosts » Removes $scope references on elements » Doesn't add classes to DOM nodes with binding info » Enable in console with angular.reloadWithDebugInfo();


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Performance driven Angular


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Understand what impacts performance before you code


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Under the hood: $digest


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$digest fundamentals » $digest loop » $$watchers ($watch) » $$asyncQueue ($evalAsync)


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$digest: $digest loop » Triggered by $scope.$apply / built-in events » Iterates $$watchers Array on $scope » If model value is different from last calculated then corresponding listener executes » Exits loop, Angular loops again (10 max) » Repaints DOM (View expressions updated)


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$digest: $$watchers » View events/bindings {{ foo }} » Angular adds a watch to the $watch list » Only $watched if bound in the View » Dirty checked in the $digest loop » Minimise use of $$watchers / avoid if possible


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$digest: $$asyncQueue » $evalAsync » Runs first in $digest » May run $digest again to flush $$asyncQueue


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track by Scenarios: * Large DOM lists * Slow DOM updates * $digests blocking UI thread (lagging)


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track by <!-- before --> <ul> <li ng-repeat="user in vm.users"> {{ user.name }} </li> </ul>


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track by <!-- after --> <ul> <li ng-repeat="user in vm.users track by user.id"> {{ user.name }} </li> </ul>


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track by » Minimal DOM repaints (only what's changed) » Uses Object references instead of Angular hashes


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ng-if / switch vs ng-show / hide <!-- ng-show --> <ul ng-show="vm.exposeNav"> <li ng-repeat="menu in vm.menus"></li> </ul> <!-- ng-if --> <ul ng-if="vm.exposeNav"> <li ng-repeat="menu in vm.menus"></li> </ul>


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ng-if / switch vs ng-show / hide » ng-if/switch reconstruct the DOM » ng-if/switch for less frequent/heavier rendering » ng-show/hide toggle "ng-hide" class » ng-show/hide for more frequent/lighter rendering » ng-show/hide less performant due to $$watchers (when hidden)


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ng-bind over {{ handlebars }} <!-- handlebars --> <p>{{ vm.username }}</p> <!-- ng-bind --> <p ng-bind="vm.username"></p> <!-- perf example --> <p> Welcome <span ng-bind="vm.username"></span> to Facebook </p>


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ng-bind over {{ handlebars }} » No DOM flicker (invisible bindings) with ng-bind » Significantly faster » ng-perf.com/2014/10/30/tip-4-ng-bind-is-fasterthan-expression-bind-and-one-time-bind » Lesser need for ng-cloak » Angular won't evaluate entire text content


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$apply or $digest? // forces a $rootScope.$digest(); $scope.$apply(); // forces a [current $scope].$digest(); $scope.$digest();


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$apply or $digest? » $scope certainties » Prevent a full $rootScope.$digest() if you're certain only child $scopes need updating » Improve performance by not forcing a full $rootScope.$digest » $scope.$digest runs on current and child $scopes » $scope.$apply triggers $rootScope.$digest call


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$destroy unbinding function myFunction () { // handle element clicks } // bind element.on('click', myFunction); // unbind $scope.$on('$destroy', function () { element.off('click', myFunction); });


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$destroy unbinding » Remove event listeners that may cause memory leaks » DOM nodes that are destroyed » Manually unbind by listening to $destroy » $scope.$on events are automatically removed


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Deep $watch vs $watchCollection var prop = [{...},{...},{...},{...}]; $scope.$watch('prop', function (newValue, oldValue) { }, true); $scope.$watchCollection('prop', function (newValue, oldValue) { });


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Deep $watch vs $watchCollection » Deep $watch uses deep Object tree comparison (expensive) » $watchCollection goes only one level deep » Shallow reference of all top level items » Try not to use either unless you have to » Not as testable » Signs of bad architecture » Litter Controllers


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avoiding DOM filters <!-- vm.date = 1444175093303 --> <p>{{ vm.date | date: 'dd-MM-yyyy' }}</p>


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avoiding DOM filters function SomeCtrl($filter) { // date passed in elsewhere var time = 1444175093303; // Parsed in JS before bound to the DOM this.parsedDate = $filter('date')(time, 'dd-MM-yyyy'); } angular .module('app') .controller('SomeCtrl', SomeCtrl);


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avoiding DOM filters <p>{{ vm.parsedDate }}</p>


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avoiding DOM filters » DOM filters run twice per $digest » Preprocess in a Controller » Bind parsed value to the View


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Takeaways » Understand the $digest loop » Investigate the performance side of each Directive/API you use » Consider using JavaScript over DOM bindings where possible ($filter etc.) » Check Angular's GitHub repo for changelogs/ releases


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Thank you @toddmotto speakerdeck.com/toddmotto


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