Zones and Change Detection
Mark Clow · Apress eBooks · 2018
Angular uses a JavaScript module called Zone.js, the purpose of which is to produce an execution context that persists across asynchronous tasks. Currently, the browser DOM and JavaScript have a limited number of asynchronous activities, such as DOM events, promises, and server calls. Zone.js can intercept these activities and give your code the opportunity to take action before and after the asynchronous activity completes. This is useful when you need to see all the information pertinent to that task, especially when an error occurs.