遍历对象数组中的嵌套对象数组

Question

尝试用所有独特的硬币制作一个 select 过滤器，但没有正确地结束。

当遍历数据时，我可以得到一个所有硬币的列表。

const uniqueCoins = data.map((item) => {
  item.currencies.map((subItem) => 
  console.log(subItem))
});

我还想使用 Set 方法和扩展运算符来获取唯一值，但我不确定如何组合所有这些。

const data = [
  {
    id: "1",
    name: "Digitec",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Bitcoin"},
      {coin: "Ethereum"},
      {coin: "XRP"},
    ],
    link: "webseite besuchen",
  },
  {
    id: "2",
    name: "Galaxus",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Bitcoin"},
      {coin: "Monero"},
      {coin: "XRP"},
    ],
    link: "webseite besuchen",
  },
  {
    id: "3",
    name: "Brack.ch",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Litecoin"},
      {coin: "Dogecoin"},
      {coin: "XRP"},
    ],
    link: "Onlineshop besuchen",
  },
];

Answer 1

const data = [
  {
    id: "1",
    name: "Digitec",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Bitcoin"},
      {coin: "Ethereum"},
      {coin: "XRP"},
    ],
    link: "webseite besuchen",
  },
  {
    id: "2",
    name: "Galaxus",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Bitcoin"},
      {coin: "Monero"},
      {coin: "XRP"},
    ],
    link: "webseite besuchen",
  },
  {
    id: "3",
    name: "Brack.ch",
    description: "Wir akzeptieren folgende Kryptowährungen",
    currencies: [
      {coin: "Litecoin"},
      {coin: "Dogecoin"},
      {coin: "XRP"},
    ],
    link: "Onlineshop besuchen",
  },
];

const uniqueCoins = [... new Set(data.map(item => item.currencies.map(subItem => subItem.coin))
                        .reduce((arr1, arr2) => arr1.concat(arr2), []))];
console.log(uniqueCoins);

Answer 2

首先使用 map, and flatMap 组合来自所有 currencies 数组的所有 coin 值，将扁平数组添加到 Set 以删除元素，然后将 Set 展开输出到数组中。

const data=[{id:"1",name:"Digitec",description:"Wir akzeptieren folgende Kryptowährungen",currencies:[{coin:"Bitcoin"},{coin:"Ethereum"},{coin:"XRP"}],link:"webseite besuchen"},{id:"2",name:"Galaxus",description:"Wir akzeptieren folgende Kryptowährungen",currencies:[{coin:"Bitcoin"},{coin:"Monero"},{coin:"XRP"}],link:"webseite besuchen"},{id:"3",name:"Brack.ch",description:"Wir akzeptieren folgende Kryptowährungen",currencies:[{coin:"Litecoin"},{coin:"Dogecoin"},{coin:"XRP"}],link:"Onlineshop besuchen"}];

// Get a new array of coins for each object, and then
// flatten all of them into one array
const coins = data.flatMap(obj => {
  return obj.currencies.map(currency => currency.coin);
});

// Create a set from the coins array
const set = new Set(coins);

// `sort and `map` over the array to produce
// an array of HTML for each option
const options = [...set].sort().map(option => {
  return `<option value=${option}>${option}</option>`;
});

// Add those options to a select
const select = `
  <select>
    <option disabled selected>Choose a coin</option>
    <option disabled>----</option>
    ${options.join('')}
  </select>
`

// Add that HTML to a container
document.body.insertAdjacentHTML('beforeend', select);

其他文档

Answer 3

使用.flatMap()方法获取硬币sub-arrays并展平数组，然后使用new Set()获取唯一值。

const data = [{id: "1",name: "Digitec",description: "Wir akzeptieren folgende Kryptowährungen",currencies: [{coin: "Bitcoin"},{coin: "Ethereum"},{coin: "XRP"}],link: "webseite besuchen"},{id: "2",name: "Galaxus",description: "Wir akzeptieren folgende Kryptowährungen",currencies: [{coin: "Bitcoin"},{coin: "Monero"},{coin: "XRP"}],link: "webseite besuchen"},{id: "3",name: "Brack.ch",description: "Wir akzeptieren folgende Kryptowährungen",currencies: [{coin: "Litecoin"},{coin: "Dogecoin"},{coin: "XRP"}],link: "Onlineshop besuchen"}];

const coins = [ ...new Set(
    data.flatMap(({currencies}) => currencies.map(({coin}) => coin))) 
];

console.log( coins );

Answer 4

您可以减少数组，然后删除重复项：

const uniqueCoins = [...new Set(data.reduce((prev, cur) => prev.concat(cur.currencies.map(cur => cur.coin)), []))]

分解：

第 1 步： 使用 array.reduce

获取数组中的所有硬币

const coins = data.reduce((prev, cur) => prev.concat(cur.currencies.map(cur => cur.coin)), []);

第 2 步：删除数组中的所有唯一值

const uniqueCoins = [...new Set(coins)];

遍历对象数组中的嵌套对象数组

Iterate through nested array of object in an Array of objects

javascript

arrays

javascript-objects

分解：