JavaScript：如何通过子对象值获取父对象键？

Question

can you help me to make a function that will be able to find parent object key by child object value?

This is object structure:

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

I tried to use this function:

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

but if I run getKeyByValue(mainObject, 'value4') it returns undefined.

Can someone help how I can improve getKeyByValue function to get the parent key (I need to get 'SECOND' name)?

Answer 1

your problem is that you check the wrong keys (objects)

 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

Doing it recursively is an option

 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);