异常捕获

定义一些HttpException类（自定义错误）：

class HttpException extends Error{
  constructor(msg = '服务器异常', errorCode = 1000, status = 500) {
    super()
    this.errorCode = errorCode
    this.status = status
    this.msg = msg
  }
}

class ParamterException extends HttpException{
  constructor(msg,  errorCode) {
    super()
    this.status = 400
    this.msg = msg || '参数错误'
    this.errorCode = errorCode || 1000
  }
}

// 上传错误
class UploadException extends HttpException{
  constructor(status, msg,  errorCode) {
    super()
    this.status = status || 400
    this.msg = msg || '上传错误'
    this.errorCode = errorCode || 1000
  }
}

定义一个catchError函数：

const { HttpException } = require("../core/http-exception");
const isDev = process.env.NODE_ENV !== "production";

const catchError = async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    const isHttpException = error instanceof HttpException;

    // 自定义错误
    if (isHttpException) {
      ctx.body = {
        msg: error.msg,
        error_code: error.errorCode,
        request: ctx.method + " " + ctx.path,
      };
      ctx.status = error.status;
      return
    }

    // 开发环境 + 非自定义的错误，抛出错误
    if (isDev) {
      throw error;
    }
    
    // 线上环境 + 非自定义的错误
    ctx.body = {
      msg: "服务器错误",
      error_code: 9999,
      request: ctx.method + " " + ctx.path,
    };
    ctx.status = 500;
  }
};

module.exports = catchError;

如何使用：

const app = new Koa()
app.use(catchError) // 在最顶部捕获