promise

// 需求：封装一个方法，给一个读取文件的路径，方法能给我们返回文件内容

const fs = require('fs')
const path = require('path')

// callback回调：第一个参数错误结果，第二个参数读取的文件内容
function getFileByPath(fpath, callback) {
    fs.readFile(fpath, 'utf-8', (err, dataStr) => {
        if (err) return callback(err)
        callback(null, dataStr)
    })
}

getFileByPath(path.join(__dirname, './package.json'), (err, dataStr) => {
    if (err) return console.log(err.message)
    //console.log(dataStr)
    console.log(JSON.parse(dataStr).name)
})

 

 

function test(resolve, reject) {
    var timeOut = Math.random() * 2;
    console.log('set timeout to: ' + timeOut + ' seconds.');
    setTimeout(function () {
        if (timeOut < 1) {
            console.log('call resolve()...');
            resolve('200 OK');
        }
        else {
            console.log('call reject()...');
            reject('timeout in ' + timeOut + ' seconds.');
        }
    }, timeOut * 1000);
}

// var p1 = new Promise(test);
// var p2 = p1.then(function (result) {
//     console.log('成功：' + result);
// });
// var p3 = p2.catch(function (reason) {
//     console.log('失败：' + reason);
// });

new Promise(test).then(res => console.log("succ")).catch(err => console.log("failed"))