操作后如何创建新对象

Question

我有一个 JavaScript 对象，如下面的可用性和保留，这里我需要从可用性中减去数量值。

var availability = {"bike":10,"cycle":3,"car":1};

var reserved ={"cycle":1,"bike":10}

我应该如何得到如下响应？

response = {"bike":0,"cycle":2,"car":1};

Answer 1

为什么不是一个简单的 for 循环。

var availability = { bike: 10, cycle: 3, car: 1 };

var reserved = { cycle: 1, bike: 10 };
let response = {};
for (let key in availability) {
  if (reserved[key]) {
    response[key] = availability[key] - reserved[key];
  } else {
    response[key] = availability[key];
  }
}

console.log(response);

输出：

{ bike: 0, cycle: 2, car: 1 }

Answer 2

您可以遍历每个键值对并用reserved 中的对应键减去availability 中的数量。然后使用Object.fromEntries() 创建您的结果对象。

const availability = { "bike" : 10, "cycle" : 3, "car" : 1 },
      reserved ={ "cycle": 1,"bike": 10 },
      result = Object.fromEntries(Object.entries(availability).map(([key, value]) => [key, value - (reserved[key] ?? 0)]));
console.log(result);

Answer 3

有很多方法可以解决这个问题，但我建议使用reduce()。

var availibilty = {
  "bike": 10,
  "cycle": 3,
  "car": 1
};

var reserved = {
  "cycle": 1,
  "bike": 10
}

function calc(a, b) {
  const answer = Object.keys(a).reduce((acc, key) => {
    return {
      ...acc,
      [key]: a[key] - (b[key] || 0)
    }
  }, {});
  console.log(answer);
}

calc(availibilty, reserved);

Answer 4

您可以循环遍历您提供的一个对象的Object. keys()，并使用 reduce() 方法减去另一个。

var availibilty = {"bike":10,"cycle":3,"car":1};
var reserved ={"cycle":1,"bike":10}


let response = Object.keys(availibilty).reduce((x, y) => {
    x[k] = availibilty[y] - reserved[y];
    return x;
}, {});

console.log(response);

Answer 5

请找到Array.reduce 实现。

逻辑

• 循环遍历availability 对象的键。
• 从reserved 对象中查找每个键的值。
• 将差异存储为accumulator 数组中相同键的值。

var availability = { "bike": 10, "cycle": 3, "car": 1 };
var reserved = { "cycle": 1, "bike": 10 };
const response = Object.keys(availability).reduce((acc, curr) => {
  acc[curr] = availability[curr] - (reserved[curr] || 0);
  return acc;
}, {});
console.log(response);