Question

在良好的云函数环境中，在request1调用内部，我能够获取bodydayOfTheWeek的输出。

但是在request1调用之外，我得到的输出未定义。

我不确定为什么。即使let变量bodydayOfTheWeek是在request1调用之外声明的。

因此不确定在请求调用中作用域变量如何工作

const request1 = require('request');  
const url = 'http://worldclockapi.com/api/json/pst/now';
let bodydayOfTheWeek: any;
request1(url, { json: true }, (err: any, res: any, body: any) => {
  if (err) { return console.log(err); }


  console.log('inside day of the week');
  bodydayOfTheWeek = body.dayOfTheWeek;
  console.log(bodydayOfTheWeek); <-- works
});

console.log('outside day of the week');
console.log(bodydayOfTheWeek);  <-- undefined

Answer 1

(err: any, res: any, body: any) => { }是异步的。因此，除非您通过回调/承诺得到bodydayOfTheWeek，否则body.dayOfTheWeek在函数外部将是未定义的。了解更多，https://javascriptissexy.com/understand-javascript-callback-functions-and-use-them/

const request = require('request');  
const url = 'http://worldclockapi.com/api/json/pst/now';

// Callback
function getDay(callback) {
    request(url, { json: true }, (err: any, res: any, body: any) => {
        if (err) {
            return callback(err);
        }

        callback(null, body.dayOfTheWeek);
    });
}

getDay((err, data) => {
    console.log(data);
});


// Promise
function getDay() {
    return new Promise((resolve, reject) => {
        request(url, { json: true }, (err: any, res: any, body: any) => {
            if (err) {
                return reject(err);
            }

            resolve(body.dayOfTheWeek);
        });
    });
}


getDa().then((data) => {
    console.log(data);
});

请求http客户端调用和变量范围

1 个答案: