JavaScript: How to get parent object key by child object value?

user_10401334 0
Viewed 615

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)?

object key javascript
2 Answers

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);

user_74942180

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'));

user_22187130
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