node[13]-回调

自定义回调函数

//自定义函数，包含回调函数
var getUser=(id,callback)=>{
  var user = {
    id:id,
    name:'jonson'
  }
  setTimeout(()=>{
    callback(user);
  },3000);
}

//调用，并且传递了一个回调函数
getUser(31,(userobject)=>{
  console.log(userobject);
})

执行后输出：

1	{ id: 31, name: 'jonson' }

天气网站回调

1	> npm install --save request

const request = require('request');

request({
  url:'https://api.openweathermap.org/data/2.5/forecast?q=beijing,cn&appid=09ec05ac89602c9970393fe760db2bf5',
  json:true   // 将json返回结果解析为json对象
},(error,response,body)=>{
  console.log(body);
});

打印出：

{ cod: '200',
  message: 0.0038,
  cnt: 38,
  list:
   [ { dt: 1542261600,
       main: [Object],
       weather: [Array],
       clouds: [Object],
       wind: [Object],
       rain: [Object],
       sys: [Object],
       dt_txt: '2018-11-15 06:00:00' },
     { dt: 1542272400,
       main: [Object],
       weather: [Array],
       clouds: [Object],
       wind: [Object],
       rain: [Object],
       sys: [Object],
       dt_txt: '2018-11-15 09:00:00' },

      ...

好看的格式显示

const request = require('request');

request({
  url:'https://api.openweathermap.org/data/2.5/forecast?q=beijing,cn&appid=09ec05ac89602c9970393fe760db2bf5',
  json:true   // 将返回结果解析为json对象
},(error,response,body)=>{
  console.log(JSON.stringify(body,undefined,2));
});

打印出：

{
  "cod": "200",
  "message": 0.0026,
  "cnt": 38,
  "list": [
    {
      "dt": 1542261600,
      "main": {
        "temp": 282.38,
        "temp_min": 277.973,
        "temp_max": 282.38,
        "pressure": 1017.9,
        "sea_level": 1043.48,
        "grnd_level": 1017.9,
        "humidity": 90,
        "temp_kf": 4.4
      },
      "weather": [
        {
          "id": 500,
          "main": "Rain",
          "description": "light rain",
          "icon": "10d"
        }
      ],
      "clouds": {
        "all": 92
      },
      "wind": {
        "speed": 1.71,
        "deg": 330.5
      },
      "rain": {
        "3h": 0.98
      },
      "sys": {
        "pod": "d"
      },
      "dt_txt": "2018-11-15 06:00:00"
    },

处理用户输入：

const request = require('request');
const yargs = require('yargs');

const argv = yargs.options({
  a:{
    demand:true,
    alias:'address',
    describe:'Address to fetch weather for',
    string:true
  }
})
.help()
.alias('help','h')
.argv;

request({
  url:`https://samples.openweathermap.org/data/2.5/forecast?q=${argv.address},cn&appid=b6907d289e10d714a6e88b30761fae22`,
  json:true   // 将返回结果解析为json对象
},(error,response,body)=>{
  console.log(JSON.stringify(body,undefined,2));
});