javascript - promise 的顺序和并行处理

Question

想法是顺序迭代数组，但并行处理子数组中的每一项。

1. 一旦记录 #1 被并行处理，它就会移动到记录 #2 并并行处理它的项目，依此类推。所以基本上它是顺序性和并行性的结合。

2. 将所有结果连接到一维数组中并显示。 (待定)

如果输入包含数组的数组。

var items = [
    ["item1", "item2"],
    ["item3", "item4"],
    ["item5", "item6"],
    ["item7", "item8"],
    ["item9", "item10"]
]

以及处理这些项目的操作。

function action(item) {
    return new Promise(function(resolve, reject){
        setTimeout(function(){
            resolve(item + ":processed");
        }, 100)
    });
}

尝试

describe("", function(){
    this.timeout(0);

    it("should", function(done){
        items.reduce(function(accumulator, currentValue, currentIndex, array){
            return accumulator.then(function(result){
                return new Promise(function(resolve, reject){
                    Promise.all(currentValue.map(action))
                        .then(resolve, reject);
                });
            });
        }, Promise.resolve())

    });

});

期望:

理想情况下，使用干净的简约和功能性方法(无状态)将结果返回给调用者。

---

尝试 2

var chain = items.reduce(function(accumulator, currentValue, currentIndex, array){
    return accumulator.then(function(result){
        return new Promise(function(resolve, reject){
            Promise.all(currentValue.map(action))
                .then(resolve, reject);
        });
    });
}, Promise.resolve());

chain.then(console.log, console.error); // I need all results here

displays last result only. [ 'item9:processed', 'item10:processed' ]

---

根据答案编辑最终解决方案。

var chain = items.reduce(function(accumulator, currentValue, currentIndex, array){
    return accumulator.then(function(result){
        return new Promise(function(resolve, reject){

            Promise.all(currentValue.map(action))
                .then(function(data){
                    resolve(result.concat(data)) // new array
                }, reject);
        });

    });
}, Promise.resolve([]));

chain.then(console.log, console.error);

Answer 1

一种方法:

var items = [
    ["item1", "item2"],
    ["item3", "item4"],
    ["item5", "item6"],
    ["item7", "item8"],
    ["item9", "item10"]
]

function action(item) {
    return new Promise(function(resolve, reject){
        setTimeout(function(){
            resolve(item + ":processed");
        }, 100)
    });
}

function process(items) {
  return items.reduce((m, d) => {
    const promises = d.map(i => action(i));
    let oldData;
    return m.then((data) => {
        oldData = data;
        return Promise.all(promises);
      })
      .then(values => {
        //oldData.push(...values);
        oldData.push.apply(oldData, values);
        return Promise.resolve(oldData);
      })
  }, Promise.resolve([]))
}

process(items).then(d => console.log(d))

//Prints:

// ["item1:processed","item2:processed","item3:processed","item4:processed","item5:processed","item6:processed","item7:processed","item8:processed","item9:processed","item10:processed"]