Why zoneJS we have in Angular?

Question

Mohd Kashif · Answer

Suppose I declared the model inside the class. And get some data from service and store into same model. So, there are some changes in model. These change in model called change detection in angular. How to handle these change in angular? This change detection is not any magic. Its handle by Zone.js (NgZone) In NgZone, there are one method - runOutsideAngular (suppose we have one rectangle and we have button on it, moving this button, coordinate get reflected. Outside we have button, on click of that button, moving should be stopped. But if you will see internally, the button is moving and coordinate is updated continuously . I hope this will be helpful.

Puneet Kankar · Answer

Hey Sanjit, A zone is an execution context that persists across async tasks and allows the creator of the zone to observe and control execution of the code within the zone. Main purpose of using zonejs in angular2 is to know when to render. For better understanding please check given below links. https://blog.bitsrc.io/how-angular-uses-ngzone-zone-js-for-dirty-checking-faa12f98cd49 https://stackoverflow.com/questions/40902572/what-is-the-use-of-zone-js-in-angular-2

Veerendra Annigere · Answer

zones are execution contexts that allow Angular to track the start and completion of asynchronous activities and perform tasks as required (e.g. change detection). Zone.js provides a global zone that can be forked and extended to further encapsulate/isolate asynchronous behaviour, which Angular does so in its NgZone service, by creating a fork and extending it with its own behaviours. Refered link : https://angular-2-training-book.rangle.io/handout/zones/

Sanjit Kumar Singh · Answer

I saw this answer in StackOverflow. https://stackoverflow.com/questions/40902572/what-is-the-use-of-zone-js-in-angular-2

Madan Shekar · Answer

It helps you see whole call stack if you face with some error. Zonejs is one of the core library used in Angularjs 2. Zonejs is to maintain contextual execution for single or multi-leveled asynchronous methods. So, it means it helps to keep track of the parent context of currently executing asynchronous method. Example code snipet Zone.current.fork({}).run(function(){ Zone.current.myZoneVar = true; console.log('Assigned myZoneVar'); setTimeout(()=>{ console.log('In timeout', Zone.current.myZoneVar); },1000); }); console.log('Out side', Zone.current.myZoneVar); Mark as answer If it helps