异常处理

局部异常处理

同步代码异常

try{}
catch(e){}

异步 Promise 代码异常

Promise.reject().then((e)=>{
})

全局异常处理

process

process.on('uncaughtException',(err)=>{

})
process.on(`unhandledRejection`,(err)=>{
})

Koa

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (err) {
  }
});

Express

```javascript
app.use((err, req, res, next) => {
  // logic
})

Nest.js

TODO: New chapter in detail

link

// http-exception.filter.ts
@Catch(HttpException)
export class HttpExceptionFilter implements ExceptionFilter {
  catch(exception: HttpException, host: ArgumentsHost) {
    const ctx = host.switchToHttp();
    const response = ctx.getResponse<Response>();
    const request = ctx.getRequest<Request>();
    const status = exception.getStatus();

    response
      .status(status)
      .json({
        statusCode: status,
        timestamp: new Date().toISOString(),
        path: request.url,
      });
  }
}

* Locally

// single route handler
@Post()
@UseFilters(new HttpExceptionFilter())
async create(@Body() createCatDto: CreateCatDto) {
  throw new ForbiddenException();
}
// every router in controller
@UseFilters(new HttpExceptionFilter())
export class CatsController {}

* Globally

  const app = await NestFactory.create(AppModule);
  app.useGlobalFilters(new HttpExceptionFilter());

---

注: 1. unhandledRejection: 每当 Promise 被拒绝并且在事件循环的一个轮询内没有错误句柄附加到承诺时，则会触发 'unhandledRejection' 事件。link 2. 在 .then(()=>{...}) 或者类似段落中出现的Excpetion且未处理可通过unhandledRejection捕获 3. 在新版本的Nodejs中(15+) Rejection 将会导致程序终止