Everything You Always Wanted to Know About AngularJS But Were Afraid to Ask

About top AngularJS caveats and bad practices.

This presentation was given during meet.js Szczecin on 10th March 2015.

1. Everything You Always Wanted to Know About AngularJS But Were Afraid to Ask
2. Michał Miszczyszyn JavaScript developer at The Comet Cult
 @mmiszy
 michal@miszczyszyn.com
3. Today’s presentation: • Top AngularJS caveats • Fixes to those caveats • … that's it!
4. ca·ve·at an explanation or warning that should be remembered when you are doing or thinking about something
5. AngularJS caveats
6. AngularJS caveats 1. project structure 2. jQuery and jqLite 3. interacting with ng 4. global services 5. service vs factory 6. $scope 7. dependency injection 8. communication
7. 1. project structure
8. project structure • at the beginning – no recommended project structure • by default apps were divided into: controllers, services, directives…
9. project structure • it's perfectly fine for small applications • The caveat: it doesn't work for larger apps • a blog post from February 2014 changed it: • https://blog.angularjs.org/2014/02/an- angularjs-style-guide-and-best.html
10. project structure e2e-tests/ sampleapp/ app.css app.js app-controller.js app-controller_test.js index.html components/ …
11. project structure components/ payments/ payments.js // module routing payments.html payments-controller.js payments-service.js payments-service_test.js payments.css
12. project structure • this approach is much cleaner • easier to find files • more flexible
13. 2. jQuery and jqLite
14. jQuery and jqLite • $ is undefined? • Error: Looking up elements via selectors is not supported by jqLite! • (even with jQuery included*)
15. jQuery and jqLite • The caveat: jqLite is not jQuery • jqLite provides a limited set of functionalities from jQuery • if you want to use jQuery, include it before angular.js file
17. jQuery and jqLite • The caveat: jqLite is not jQuery • jqLite provides a limited set of functionalities from jQuery • if you want to use jQuery, include it before angular.js file
18. jQuery and jqLite • angular.js before jquery.js: $('#home')//ok
 angular.element('#home')//nope
19. jQuery and jqLite • angular.js after jquery.js: $('#home')//ok
 angular.element('#home')//ok • all elements wrapped in jQuery
20. 3. interacting with ng
21. interacting with ng • Angular makes a lot of things easier • (duh) • The caveat: for anything to work with Angular it has to be done
 The Angular Way®
22. interacting with ng • many people ask why this won't work $('input') .attr('ng-model', 'name'); • you shouldn't try to interact with Angular from the outside • use directives instead
23. 4. global services
24. global services • you can use any other libraries with Angular • The caveat: You should wrap them in angular service
25. global services • eg. Underscore • you can simply access it in your controllers: app.controller('Ctrl', function(){
 _.partition(…);
 }); • but it's wrong!
26. global services • much harder to write unit tests • impossible to change the implementation • you want to use DI for this
27. global services app.controller('Ctrl',function(_){
 _.partition()
 });
 app.factory('_',function($window){
 return $window._;
 });
28. 5. service vs factory
29. service vs factory • angular brings a lot of new concepts • one of them are services, factories and providers • the caveat: many people find it hard to understand how to use them
31. service vs factory • factory expects a function as an argument • service expects a constructor • provider is more complicated • all return singletons
32. service vs factory app.factory('a', fna);
 app.service('b', fnb);
 app.provider('c', fnc); 
 a = fna(); b = new fnb(); c = (new fnc()).$get();
33. service vs factory app.factory('myFactory', function() { return { sayHello: function(name) { return "Hello world " + name; }
 }
 });
34. service vs factory app.service('myService', function() { this.sayHello = function(name) { return "Hello world " + name; };
 });
35. service vs factory • usually all you need is just a service
36. 6. $scope
37. $scope • The caveat: everything • a "mystical" object • there's a lot of confusion about it • quick example
38. $scope {{myVar}}
 <div>
 <input ng-model="myVar">
 </div> • if you type in the input, the text shows above
39. $scope {{myVar}}
 <div ng-show="isVisible">
 <input ng-model="myVar">
 </div> • …this still works…
40. $scope {{myVar}}
 <div ng-if="isVisible">
 <input ng-model="myVar">
 </div> • …and this doesn't!
42. $scope • ng-if creates a child scope • ng-show doesn't • it's not intuitive at all!
43. $scope • authors of Angular used to advice: • ”if you use ng-model there has to be a dot somewhere. If you don't have a dot, you're doing it wrong”
44. $scope {{a.b}}
 <div ng-if="isVisible">
 <input ng-model="a.b">
 </div> 
 $scope.a = {};
45. $scope • more generic solution • property on the scope: $scope.MyCtrl = $scope;
 <input ng-model="MyCtrl.x">
46. $scope • this solution is ugly and there's still room for bugs • …so what's $scope even for? • ? • we can do without it!
47. $scope • controller as syntax <div ng-controller="MyCtrl"> <div ng-controller="MyCtrl as myCtrl"> • local name for controller object • let's fix the previous example!
48. $scope {{myCtrl.myVar}}
 <div ng-if="myCtrl.isVisible">
 <input ng-model="myCtrl.myVar">
 </div>
49. $scope app.controller('MyCtrl', function() {
 this.isVisible = true;
 }); • no more $scope! • use this – feels more like JavaScript
50. 7. dependency injection
51. dependency injection • one of the best things in Angular • cleaner code • easier to test
52. dependency injection app.controller('MyCtrl', function($timeout) {
 // $timeout is injected!
 }); • very simple to use • angular can inject based on argument name
53. dependency injection • The caveat: minification app.controller("MyCtrl",function(a){}); • Unknown provider: aProvider
54. COULD YOU NOT?
55. dependency injection • there are different solutions: • not to minify parts of files • use array notation: ["$timeout",function($timeout){}] • use ng-annotate – does this automatically
56. 8. communication
57. communication • often in the application you need to communicate between components • the caveat: Angular doesn't provide good means to do that
58. communication • there are a few builtin solutions: • $broadcast • $rootScope • $watch
59. communication • Which should be used to communicate between controllers? • None.
61. communication • $brodcast – often abused • $broadcast('myCtrl:sth') – don't! • use only for events that are relevant to the whole application • login, closing the app etc…
62. communication • $rootScope – often abused… • $rootScope.sth = 123 – don't! • it's as bad as global variables • use for configuration settings or things like page title
63. communication • $watch – often abused… • $watch(() => { MyService; }, …) • the rule of thumb: limit its usage to a minimum • makes testing much harder • might be bad for performance
64. communication • good solution: use a shared service • straighforward to use to just share data between controllers • simply store the data or functions
65. communication app.service('AuthStore', function (){
 this.getUser = function () { … };
 this.storeUser = function () { … };
 });
66. communication • good solution: observer pattern • well known • easy to implement • no performance hit • good for observing changes in the data
67. communication AuthStore.addObserver(doSomething);
 $scope.$on('$destroy', function () { AuthStore.removeObserver(doSomething); });
68. Sources: • http://stackoverflow.com/questions/20369514/building-a-web-app-in-angularjs-without-jquery • https://www.airpair.com/angularjs/posts/top-10-mistakes-angularjs-developers-make • http://www.bennadel.com/blog/2752-using-jquery-instead-of-jqlite-in-angularjs.htm • https://blog.angularjs.org/2014/02/an-angularjs-style-guide-and-best.html • https://docs.google.com/document/d/1XXMvReO8- Awi1EZXAXS4PzDzdNvV6pGcuaF4Q9821Es/pub • http://toddmotto.com/digging-into-angulars-controller-as-syntax/ • http://stackoverflow.com/questions/12008908/how-can-i-pass-variables-between-controllers • http://stackoverflow.com/questions/13762228/confused-about-service-vs-factory/ 13763886#13763886 • http://giphy.com/search/looney-tunes/5
69. Michał Miszczyszyn JavaScript developer at The Comet Cult
 @mmiszy
 michal@miszczyszyn.com
70. AngularJS caveats
71. Thank you!
72. Questions?