有没有更高阶的函数从javascript中的对象数组返回一个对象？ [英] Are there any higher order function to return an object from an array of objects in javascript?

问题描述

背景

尝试学习javascript的高阶函数，一些redux理论，并通过数据转换示例应用它，在过去几个小时里一直都失败了。 ：（

Trying to learn javascript's higher order function, some redux theory and applying it through a data transformations example and have been failing for the last few hours. :(

问题：

如何迭代 approved1 或 approved2 ，并返回一个基于 2个的新对象，此外，有没有办法使用更高级的函数，如 Array.reduce（）或在较高阶函数中组合的组合？最后，如果最终的对象被包装

How can I iterate over the approved1 or approved2 and return a new object bases on 2 cases. Furthermore, is there a way to do this with a higher order function like Array.reduce() or a combination baked in higher order functions? Lastly, if the final Object is wrapped in an array thats fine too.

我想要这个原因有以下几点：

I want this for a few reasons:

<

• 易于测试


• 学习目的

2例：

• 如果全部 dateApproved 值是！== null （在这个例子中： approval1 array）然后返回一个新的Object （或Array wrapped Object），如下所示：

• If all dateApproved values are !== null (in this example: approval1 array) then return a new Object (or Array wrapped Object) which looks like:

{type ：已批准，批准：[... approved1]}

如果 dateApproved 中的任何值等于 null （在本示例中为 approval2 array）返回一个新的Object （或Array wrapped Object），如下所示：

If any of the dateApproved values are equal to null (in this example: approval2 array) return a new Object (or Array wrapped Object) which looks like:

{type：'PENDING'，approval：[... approved2]}

JAVASCRIPT：

// With given logic this array evaluate with a type of 'APPROVED'
var approved1 = [

    {
        dateApproved: new Date(),
        id: 1,
    },
    {
        dateApproved: new Date(),
        id: 2,
    }
];

// With given logic this array evaluate with a type of 'PENDING'
var approved2 = [

    {
        dateApproved: null,
        id: 1,
    },
    {
        dateApproved: new Date(),
        id: 2,
    }
];

// This reducer does nothing proper right now just placeholder.
function isApproved(previousValue, currentValue, currentIdx) {
    var TYPE = ['APPROVED', 'PENDING'];
    if(previousValue.dateApproved !== null && currentValue.dateApproved !== null) {

      return currentValue
    }
}

var x = approved1.reduce(isApproved);
console.log(x); // LOG: {type: 'APPROVED' approvals: [...approved1]}

var y = approved2.reduce(isApproved);
console.log(x); // LOG: {type: 'PENDING' approvals: [...approved2]}

推荐答案

使用数组。 prototype.every ：

function wrap(approvals) {
  return {
    type: approvals.every(a => a.dateApproved != null) ? 'APPROVED' : 'PENDING',
    approvals: approvals
  };
}

wrap(approved1);
// => Object {type: "APPROVED", approvals: Array[2]}

wrap(approved2);
// => Object {type: "PENDING", approvals: Array[2]}

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