阿里笔试题目 -- 实现mergePromise函数

实现mergePromise函数，把传进去的数组顺序先后执行,并且把返回的数据先后放到数组data中.

//实现mergePromise函数，把传进去的数组顺序先后执行，
//并且把返回的数据先后放到数组data中

const timeout = ms => new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve();
    }, ms);
});

const ajax1 = () => timeout(2000).then(() => {
    console.log('1');
    return 1;
});

const ajax2 = () => timeout(1000).then(() => {
    console.log('2');
    return 2;
});

const ajax3 = () => timeout(2000).then(() => {
    console.log('3');
    return 3;
});

const mergePromise = ajaxArray => {
    // 在这里实现你的代码
    var data = [];
    var sequence = Promise.resolve();
    ajaxArray.forEach(function(item){
        sequence = sequence.then(item).then(function(res){
             data.push(res);
             return data;
        }); 
    })

    return sequence;
};

mergePromise([ajax1, ajax2, ajax3]).then(data => {
    console.log('done');
    console.log(data); // data 为 [1, 2, 3]
});

// 分别输出
// 1
// 2
// 3
// done
// [1, 2, 3]