有条件地操作数组中元素的属性

Question

我是 javascript 新手，正在尝试通过玩具示例学习一些基础知识。

假设我有一个包含六个人数据的数组。

const myArray = [
    {"id": 1, "value": 75, "friends": 3},
    {"id": 2, "value": 40, "friends": 4},
    {"id": 3, "value": 60, "friends": 5},
    {"id": 4, "value": 62, "friends": 6},
    {"id": 5, "value": 55, "friends": 1},
    {"id": 6, "value": 33, "friends": 2}
];

该数组列出了每个人的id、value，以及他们与谁friends。例如，第 1 个人是第 3 个人的朋友，第 3 个人是第 5 个人的朋友，依此类推。

现在我想根据每个人的价值来操纵谁和谁成为朋友。这是我想要实现的逻辑（可能在 for 循环中）：

IF人的值是数组中最低的或次低的值， THEN 将数组中具有 最高 值的人的 id 添加到他们的朋友。

所以在这种情况下我想要的输出是：

const myArray = [
    {"id": 1, "value": 75, "friends": 3},
    {"id": 2, "value": 40, "friends": [4, 1]},
    {"id": 3, "value": 60, "friends": 5},
    {"id": 4, "value": 62, "friends": 6},
    {"id": 5, "value": 55, "friends": 1},
    {"id": 6, "value": 33, "friends": [2, 1]}
];

我该怎么做？

---

我已经对下面的数组进行了非常基本的操作，在这里我带走了数组中值最高的人的朋友。但是当我开始从事这项更复杂的任务时，我感到很困惑。

const myArray = [
    {"id": 1, "value": 75, "friends": 3},
    {"id": 2, "value": 40, "friends": 4},
    {"id": 3, "value": 60, "friends": 5},
    {"id": 4, "value": 62, "friends": 6},
    {"id": 5, "value": 55, "friends": 1},
    {"id": 6, "value": 33, "friends": 2}
];

// Finds max and min values in array
var highest = Number.NEGATIVE_INFINITY;
var tmp;
for (var i=myArray.length-1; i>=0; i--) {
    tmp = myArray[i].value;
    if (tmp > highest) highest = tmp;
};

for(i = 0; i < myArray.length; i++){
    // If person has the highest value in the array
      if(myArray[i].value == highest){
        // Then take away their friend
        myArray[i].friends = NaN
      } else {
        myArray[i].friends = myArray[i].friends
      }
  };

  console.log(myArray);

Answer 1

您可以通过一次源数组来计算出最高值、最低值和次低值（以及对应的id），然后在到达末尾时相应地修改源数组：

const src = [
    {"id": 1, "value": 75, "friends": 3},
    {"id": 2, "value": 40, "friends": 4},
    {"id": 3, "value": 60, "friends": 5},
    {"id": 4, "value": 62, "friends": 6},
    {"id": 5, "value": 55, "friends": 1},
    {"id": 6, "value": 33, "friends": 2}
],
    
    populateFriends = input => {
      let highest = {value: -Infinity},
          lowest = {value: Infinity},
          secondLowest = {}
      for({id, value} of input){
          if(value > highest.value){
            highest = {id, value}
          } else if(value < lowest.value){
            secondLowest = {...lowest}
            lowest = {id, value}
          }
      }
      return input.map(o => 
        (o.id == lowest.id || o.id == secondLowest.id) && 
        o.friends != highest.id ? 
        {...o, friends: [o.friends, highest.id]} :
        o)
    }
    
console.log(populateFriends(src))

.as-console-wrapper{min-height:100%;}

Answer 2

你可以这样做

const myArray = [
    {"id": 1, "value": 75, "friends": 3},
    {"id": 2, "value": 40, "friends": 4},
    {"id": 3, "value": 60, "friends": 5},
    {"id": 4, "value": 62, "friends": 6},
    {"id": 5, "value": 55, "friends": 1},
    {"id": 6, "value": 33, "friends": 2}
];

const highestValue = myArray.reduce((acc, rec) => {
  return (acc.value < rec.value) ? acc = rec : acc
}, myArray[0])

const twoLowestPersons = myArray.sort((a, b) => a.value - b.value).slice(0, 2)

const result = myArray.map(rec => {
  const object = twoLowestPersons.find(el => el.id === rec.id)
  if (typeof object !== 'undefined') {
    rec.friends = [rec.friends, highestValue.id]
    return rec
  } else {
    return rec
  }
}).sort((a, b) => a.id - b.id)

console.log(JSON.stringify(result))