Why zoneJS we have in Angular?

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/

Hey Sanjit,

 

I saw this answer in StackOverflow.

https://stackoverflow.com/questions/40902572/what-is-the-use-of-zone-js-in-angular-2 

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