JavaScript：如何通過子對象值獲取父對象鍵？

Question

你能幫我做一個能夠通過子對象值找到父對象鍵的函數嗎？

這是對象結構：

const mainObject = {
  FIRST: {
    key1: 'value1',
    key2: 'value2',
  },
  SECOND: {
    key3: 'value3',
    key4: 'value4',
  },
};

我嘗試使用此功能：

function getKeyByValue(object, value) {
  return Object.keys(object).find((key) => object[key] === value);
}

但是如果我運行getKeyByValue(mainObject, 'value4')它返回未定義。

有人可以幫助我如何改進 getKeyByValue 函數以獲取父鍵（我需要獲取“第二個”名稱）？

Answer 1

你的問題是你檢查了錯誤的鍵（對象）

 const mainObject = { FIRST: { key1: 'value1', key2: 'value2', }, SECOND: { key3: 'value3', key4: 'value4', }, }; function getKeyByValue(object, value) { //you can see that the first keys are for the first objects (first and second) this method doesnt give nested keys. console.log(Object.keys(object)); return Object.keys(object).find((key) => Object.keys(object[key]).some((key2) => object[key][key2] === value)); } //you can also do this and check directly the values function getKeyByValue2(object, value) { //you can see that the first keys are for the first objects (first and second) this method doesnt give nested keys. console.log(Object.keys(object)); return Object.keys(object).find((key) => Object.values(object[key]).indexOf(value) > -1); } console.log(getKeyByValue(mainObject, 'value4')); console.log(getKeyByValue2(mainObject, 'value4'));

Answer 2

遞歸執行是一種選擇

 let path = []; let parent = ''; function getParent(path, json, value) { for (var key in json) { if (typeof json[key] === 'object') { path.push(key.toString()); getParent(path, json[key], value); path.pop(); } else { if (json[key] == value) { parent = path[0]; } } } } const mainObject = { FIRST: { key1: 'value1', key2: 'value2', }, SECOND: { key3: 'value3', key4: 'value4', }, }; getParent(path, mainObject, 'value4'); console.log(parent);