javascript - 当 json 具有同名键时，new Map() 如何在 javascript 中工作

Question

我有一个 JSON 结构和如下代码:

const villages = 
{
"lossesOccured":
    [
        {
            "type": "destroyed",
            "affectedOn": "humans",
            "quantity": 120,
            "reliefFund": 100000,
            "location": {
                "district": "thanjavur",
                "villageName": "madukkur",
                "pincode": "614903"
            }
        },
        {
            "type": "physicalDamage",
            "affectedOn": "humans",
            "quantity": 250,
            "reliefFund": 50000,
            "location": {
                "district": "thanjavur",
                "villageName": "madukkur",
                "pincode": "614903"
            }
        },
    ]
}

const lossesArray = villages.lossesOccured

let myMap = new Map()

lossesArray.forEach(loss => {
    if(loss.affectedOn === "humans"){
        myMap.set(loss.affectedOn,loss)
    }
})

 console.log(myMap)

初始化一个新的 map 并为其分配键值。关键是“受影响”。由于在许多元素中有相同的键名(affectedOn)，map 消除了所有重复项并只打印一个。有没有办法打印所有键值，即使它具有相同的名称。提前致谢。

输出:

Answer 1

Map 具有键值对，类似于对象，并且每个 distinct 键都有一个值。 (如果你想使用键 k1 和 k2，以及 k1 === k2，你调用 myMap.set(k1 然后是myMap.set(k2，那么k1赋的初始值会被覆盖。)

如果您想将输入数组中的所有内容 转换为Map，确保键唯一的一种方法是将键设为对象(彼此不会是===):

myMap.set({ key: loss.affectedOn }, loss);

const villages = {
  "lossesOccured": [{
      "type": "destroyed",
      "affectedOn": "humans",
      "quantity": 120,
      "reliefFund": 100000,
      "location": {
        "district": "thanjavur",
        "villageName": "madukkur",
        "pincode": "614903"
      }
    },
    {
      "type": "physicalDamage",
      "affectedOn": "humans",
      "quantity": 250,
      "reliefFund": 50000,
      "location": {
        "district": "thanjavur",
        "villageName": "madukkur",
        "pincode": "614903"
      }
    },
  ]
}

const lossesArray = villages.lossesOccured

const myMap = new Map();
lossesArray.forEach(loss => {
  if (loss.affectedOn === "humans") {
    myMap.set({ key: loss.affectedOn }, loss);
  }
});

console.log(myMap);