将类型引用为索引时出错

Question

我有一个具有以下结构的对象数组

let sampleData = [
    { valueObj: { High: 4, Low: 5,  Medium: 7 } , time: "1571372233234" , sum: 16 },
    { valueObj: { High: 5, Low: 3, Medium : 1 }, time: "1571372233234" , sum: 9},
    { time: "14354545454", sum: 0},
    { time: "14354545454", sum: 0} }
];

我需要获取数组中每个对象中的每个键并从中形成一个数组。基本上根据所有 objects.If 中存在的键进行分组对象没有 "values" 它应该 return 0 跨越 val1,val2,val3.

result = [
  { name: 'High', data: [4, 5, 0, 0] }, 
  { name: 'Medium', data: [5, 3, 0, 0] }, 
  { name: 'Low', data: [7, 1, 0, 0] }
];

我在这里传递一个字符串，它将在内部使用 reduce.I 收到此错误 any cannot be used as index 每当我传入一个动态字符串时只要启用打字稿，就会在 reduce 函数中使用。

代码工作正常，但在我升级到最新的 TS 后它抛出错误并且无法编译

有人可以帮助我吗？

我试过以下方法：

const sampleData = [{ valueObj: { High: 4, Low: 5,  Medium: 7 }, time: "1571372233234", sum: 16 }, { valueObj: { High: 5, Low: 3, Medium : 1 }, time: "1571372233234", sum: 9 }, { time: "14354545454", sum: 0 }, { time: "14354545454", sum: 0 }];

const keys = ['High', 'Low', 'Medium'];

function formResult(sampleData, prop, keys){
  let grouped = sampleData.reduce((r, { [prop]: values = {} } = {}) => {
    r.forEach(({ name, data }) => data.push(values[name] || 0));       
    return r;
  }, keys.map(name => ({ name, data: [] })));
  console.log(grouped);
}

formResult(sampleData,"valueObj", keys);

Answer 1

该函数未返回 grouped。这可能是问题所在

const sampleData = [{
  valueObj: {
    High: 4,
    Low: 5,
    Medium: 7
  },
  time: "1571372233234",
  sum: 16
}, {
  valueObj: {
    High: 5,
    Low: 3,
    Medium: 1
  },
  time: "1571372233234",
  sum: 9
}, {
  time: "14354545454",
  sum: 0
}, {
  time: "14354545454",
  sum: 0
}];

const keys = ['High', 'Low', 'Medium'];

function formResult(sampleData, prop, keys) {
  return sampleData.reduce((r, {
    [prop]: values = {}
  } = {}) => {
    r.forEach(({
      name,
      data
    }) => data.push(values[name] || 0));
    return r;
  }, keys.map(name => ({
    name,
    data: []
  })));

}

console.log(formResult(sampleData, "valueObj", keys));

Answer 2

在 Typescript 中使用带有动态键的 reduce 可能很丑陋，并且在创建单个对象时是 arguably not appropriate even in Javascript。考虑创建将数据放入循环外部的对象 - 一个属性是名称（高等）并且值是数字数组的对象。在每次迭代时推送到数字数组（如果属性不存在，则推送 0），如果需要，首先使用数组创建属性。循环后，将对象转为对象数组：

// compliant with noImplicitAny and strict options
type DataItem = {
    time: string;
    sum: number;
    valueObj?: {
        High: number;
        Medium: number;
        Low: number;
    }
};
const sampleData: DataItem[] = [
    { valueObj: { High: 4, Low: 5,  Medium: 7 } , time: "1571372233234" , sum: 16 },
    { valueObj: { High: 5, Low: 3, Medium : 1 }, time: "1571372233234" , sum: 9},
    { time: "14354545454", sum: 0},
    { time: "14354545454", sum: 0}
];
const keys = ['High', 'Low', 'Medium'] as const;
const grouped = {} as { [key: string]: number[] };
for (const item of sampleData) {
    for (const key of keys) {
        if (!grouped[key]) {
            grouped[key] = [];
        }
        grouped[key].push(item.valueObj ? item.valueObj[key] : 0);
    }
}
const output = Object.entries(grouped).map(([name, data]) => ({ name, data }));

编译输出：

"use strict";
const sampleData = [
    { valueObj: { High: 4, Low: 5, Medium: 7 }, time: "1571372233234", sum: 16 },
    { valueObj: { High: 5, Low: 3, Medium: 1 }, time: "1571372233234", sum: 9 },
    { time: "14354545454", sum: 0 },
    { time: "14354545454", sum: 0 }
];
const keys = ['High', 'Low', 'Medium'];
const grouped = {};
for (const item of sampleData) {
    for (const key of keys) {
        if (!grouped[key]) {
            grouped[key] = [];
        }
        grouped[key].push(item.valueObj ? item.valueObj[key] : 0);
    }
}
const output = Object.entries(grouped).map(([name, data]) => ({ name, data }));
console.log(output);

如果 valueObj 键是动态的，它会变得更丑陋。我能弄清楚的是，在遍历数组项时，如果它具有自己的属性对象键，则断言数组项的类型为 { [possibleKeyForObj: string]: { [key: string]: number } }，从而允许您访问嵌套属性:

const formResult = (
    sampleData: object[],
    possibleKeyForObj: string,
    keys: string[],
) => {
    const grouped = Object.fromEntries(keys.map(key => [key, []]));
    for (const item of sampleData) {
        for (const key of keys) {
            grouped[key].push(
                item.hasOwnProperty(possibleKeyForObj)
                    ? (item as { [possibleKeyForObj: string]: { [key: string]: number } })[possibleKeyForObj][key]
                    : 0,
            );
        }
    }
    const output = Object.entries(grouped).map(([name, data]) => ({ name, data }));
    console.log(output);
};

formResult(
    [
        { valueObj: { High: 4, Low: 5, Medium: 7 }, time: '1571372233234', sum: 16 },
        { valueObj: { High: 5, Low: 3, Medium: 1 }, time: '1571372233234', sum: 9 },
        { time: '14354545454', sum: 0 },
        { time: '14354545454', sum: 0 },
    ],
    'valueObj',
    ['High', 'Low', 'Medium'],
);

将类型引用为索引时出错

Getting error while referencing the type as index

javascript

ecmascript-5

typescript

ecmascript-6

ecmascript-2016