用位置替换数组中的对象答案

【问题标题】：Replacing an object in an array with places用位置替换数组中的对象
【发布时间】：2019-04-15 16:57:08
【问题描述】：

该函数将一个对象添加到数组中，并使其在列表中排在第二位。但在这种情况下，我紧紧抓住对象，我知道他创建后的编号是多少（5）。如何让它总是第二个添加？

const arr = [{
    "name": "BMW",
    "price": "55 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mercedes-benz",
    "price": "63 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mitsubishi",
    "price": "93 000",
    "constructor": "Bar John",
    "door": "3",
    "country": "Japan",
  },
  {
    "name": "TOYOTA",
    "price": "48 000",
    "max_people": "7",
    "country": "Japan",
    "certificate": "yes"
  },
  {
    "name": "Volkswagen",
    "price": "36 000",
    "constructor": "Pier Sun",
    "country": "Germany",
    "certificate": "no"
  },
];

function pushArr(arr, item) {
  arr.push(item);
  arr[5] = [arr[1], arr[1] = arr[5]][0];
}

let newArr = pushArr(arr, {
  "name": "Audi",
  "price": "89 000",
  "constructor": "Adolf Trump",
  "country": "Germany",
  "certificate": "yes"
});

console.log(arr);

【问题讨论】：

请查看this post

标签： javascript arrays methods

【解决方案1】：

const arr = [{
    "name": "BMW",
    "price": "55 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mercedes-benz",
    "price": "63 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mitsubishi",
    "price": "93 000",
    "constructor": "Bar John",
    "door": "3",
    "country": "Japan",
  },
  {
    "name": "TOYOTA",
    "price": "48 000",
    "max_people": "7",
    "country": "Japan",
    "certificate": "yes"
  },
  {
    "name": "Volkswagen",
    "price": "36 000",
    "constructor": "Pier Sun",
    "country": "Germany",
    "certificate": "no"
  },
];

function pushArr(arr, item) {
  let n = arr.length;
  arr.push(item);
  arr[n] = [arr[1], arr[1] = arr[n]][0];
}

let newArr = pushArr(arr, {
  "name": "Audi",
  "price": "89 000",
  "constructor": "Adolf Trump",
  "country": "Germany",
  "certificate": "yes"
});

let newArr2 = pushArr(arr, {
  "name": "Audi2",
  "price": "100 000",
  "constructor": "Adolf Trump",
  "country": "Germany",
  "certificate": "yes"
});

console.log(arr);

【讨论】：

【解决方案2】：

您可以使用destructuring assignment 获取变量中的第一个和剩余元素，然后将传入的值放在第二个位置返回新数组

const arr = [{"name": "BMW","price": "55 000","country": "Germany","certificate": "yes"},{"name": "Mercedes-benz","price": "63 000","country": "Germany","certificate": "yes"},
{"name": "Mitsubishi","price": "93 000","constructor": "Bar John","door": "3","country": "Japan" },
 {"name": "TOYOTA","price": "48 000","max_people": "7","country": "Japan","certificate": "yes"},
{"name": "Volkswagen","price": "36 000","constructor": "Pier Sun","country": "Germany","certificate": "no"},];

let atSecondAlways = (arr,newValue) => {
  let [first, ...remaining] = arr
  return [first,newValue,...remaining]
}

let newArr = atSecondAlways(arr,{ "name": "Audi", "price": "89 000",  "constructor": "Adolf Trump", "country": "Germany", "certificate": "yes"});

console.log(newArr);

【讨论】：

【解决方案3】：

你可以使用 Array.splice()。使用此方法，您可以向数组添加或删除项目。

请小心，因为拼接会影响原始数组，因此在应用更改之前创建数组的副本很方便

function pushArr(arr, item) {
  let newArr = [...arr]
  newArr.splice(1,0,item);
  return newArr;
}

【讨论】：

【解决方案4】：

您可以使用解构。顺便别忘了返回数组

const arr = [{
    "name": "BMW",
    "price": "55 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mercedes-benz",
    "price": "63 000",
    "country": "Germany",
    "certificate": "yes"
  },
  {
    "name": "Mitsubishi",
    "price": "93 000",
    "constructor": "Bar John",
    "door": "3",
    "country": "Japan",
  },
  {
    "name": "TOYOTA",
    "price": "48 000",
    "max_people": "7",
    "country": "Japan",
    "certificate": "yes"
  },
  {
    "name": "Volkswagen",
    "price": "36 000",
    "constructor": "Pier Sun",
    "country": "Germany",
    "certificate": "no"
  },
];

function pushArr(arr, item) {
  const [first, ...rest] = arr;
  return [first, item, ...rest ];
}

let newArr = pushArr(arr, {
  "name": "Audi",
  "price": "89 000",
  "constructor": "Adolf Trump",
  "country": "Germany",
  "certificate": "yes"
});

console.log(newArr);

【讨论】：