將陣列保存為鍵中的值并回圈遍歷它們以獲取鍵-有解無憂

如果我輸入任何變數，我希望能夠使用 getValue 并迭代 myObject 鍵來獲取鍵值“f”。

result = "f";

或者

result = " g";

const myObject = {
  "f": [1, 2, 3, 4, 5],
  "g": [6, 7, 8, 9, 10]
};
let getValueOne = 1;

function getKeyByValue() {
  for (let i = 0; i < myObject[value].length; i  ) {
    result = myObject.key[i];
    if (i === getValueOne) {
      console.log(result);
    }
  }
}

uj5u.com熱心網友回復：

你的意思是找到哪個陣列包含值的鍵？

const getByValue = (obj,val) => Object.entries(obj)
  .filter(([key,arr]) => arr.includes(val))
  .map(([key,arr]) => key)[0] ?? "N/A";
const myObject = {
  "f": [1, 2, 3, 4, 5],
  "g": [6, 7, 8, 9, 10]
};
console.log(getByValue(myObject,1))
console.log(getByValue(myObject,99))
console.log(getByValue(myObject,6))

選擇

const getByValue = (obj,val) => Object.entries(obj)
  .reduce((acc,[key,arr]) => (arr.includes(val) && acc.push(key),acc),[])[0] ?? "N/A";
  
const myObject = {
  "f": [1, 2, 3, 4, 5],
  "g": [6, 7, 8, 9, 10]
};
console.log(getByValue(myObject,1))
console.log(getByValue(myObject,99))
console.log(getByValue(myObject,6))

使用查找表（靈感來自vitaly-t 的回答）

這是假設所有陣列中的唯一值

const makeLookup = obj => Object.entries(obj).reduce((acc,[key,arr]) => (arr.forEach(val => acc[val] = key),acc),{});
const getByValue = (tbl,val) => tbl[val] ?? "N/A";
const myObject = {
  "f": [1, 2, 3, 4, 5],
  "g": [6, 7, 8, 9, 10]
};

const lookUp = makeLookup(myObject);
console.log(JSON.stringify(lookUp))

console.log(getByValue(lookUp,1))
console.log(getByValue(lookUp,99))
console.log(getByValue(lookUp,6))

uj5u.com熱心網友回復：

@mplungjans 回答使用Array.find

const getByValue = (obj, val) => 
(Object.entries(obj).find(([key, arr]) => 
   arr.find(v => val === v)) || [`N/A`]).shift();
const myObject = {
  f: [1, 2, 3, 4, 5],
  g: [6, 7, 8, 9, 10]
};
console.log(getByValue(myObject,1))
console.log(getByValue(myObject,99))
console.log(getByValue(myObject,6))

uj5u.com熱心網友回復：

如果訪問同一物件的速度很重要，那么最好Map先從該物件創建一個，然后您可以立即檢索每個值：

const myObject = {
    "f": [1, 2, 3, 4, 5],
    "g": [6, 7, 8, 9, 10]
};

const qm = new Map(Object.entries(myObject)
                   .flatMap(([key, val]) => val.map(a => ([a, key]))));

const getByValue = (val) => qm.get(val) ?? 'N/A';

console.log(getByValue(1)); //=> f
console.log(getByValue(99)); //=> N/A
console.log(getByValue(6)); //=> g

如果某些值在陣列中不是唯一的，則后面的每個值都將覆寫前一個值。

顯示代碼片段

const myObject = {
"f": [1, 2, 3, 4, 5],
"g": [6, 7, 8, 9, 10]
};

const qm = new Map(Object.entries(myObject)
.flatMap(([key, val]) => val.map(a => ([a, key]))));

const getByValue = (val) => qm.get(val) ?? 'N/A';

console.log(getByValue(1));
console.log(getByValue(99));
console.log(getByValue(6));

轉載請註明出處，本文鏈接：https://www.uj5u.com/ruanti/534276.html

標籤：javascript查询数组循环目的

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