Asynchronous handlers
All of the examples shown so far in this chapter assume that handlers are synchronous. In a real application, many handlers will need to be asynchronous.
Nest.js provides a number of approaches to write asynchronous request handlers.
Async/await
Nest.js has support for async request handler functions.
In our example application, the entriesService.findAll() function actually returns a Promise<Entry[]>. Using async and await, this function could be written as follows.
import{Controller,Get}from'@nestjs/common';@Controller('entries')exportclassEntryController{@Get()asyncindex():Promise<Entry[]>{constentries:Entry[]=awaitthis.entryService.findAll();returnentries;}
Async functions have to return promises, but using the async/await pattern in modern JavaScript, the handler function can appear to be synchronous. Next, we’ll resolve the returned promise and generate the response...