ES6—43：Promise

const p = new Promise((resolve,reject) => {
    // 1. 创建对象
    const xhr = new XMLHttpRequest();
    // 2. 初始化
    xhr.open("GET","https://api.apiopen.top/getJoke");
    // 3. 发送
    xhr.send();
    // 4. 绑定事件，处理响应结果
    xhr.onreadystatechange = function() {
        if (xhr.readyState === 4) {
            if (xhr.status >= 200 && xhr.status <= 300) {
                resolve(xhr.response);
            } else {
                reject(xhr.status);
            }
        }
    }
});
p.then(function(value) {
    console.log(value);
},function(reason) {
    console.log(reason);
});

// 首先，引入fs模块
const fs = require('fs');
const p = new Promise((resolve,reject) => {
    fs.readFile("./test.md",(err,data) => {
        resolve(data);
    });
});
p.then((value) => {
    return new Promise((resolve,reject) => {
        fs.readFile("./木言人.md",(err,data) => {
            resolve([value,data]);
        });
    });
}).then((value) => {
    return new Promise((resolve) => {
        fs.readFile("./读书有感.md",(err,data) => {
            value.push(data);
            resolve(value);
        });
    });
}).then((value) => {
    console.log(value.toString());
});