I want to return a key using Lodash when it contains a particular value

Question

I have an object like this:

const obj = {
  'MONEY-OUT': {
    USD: ['a', 'b', 'c'],
    EUR: ['d', 'e', 'f'],
  },
  'MONEY-IN': {
    USD: ['g', 'h', 'i'],
    EUR: ['j', 'k', 'l'],
  },
};

and I want to create a function that returns either the key MONEY-OUT / MONEY-IN if that key contains a character in its array using Lodash. I have 2 variables in this function: currency, search_string

For example, my variable values for this function are 'EUR' and 'k' so I need my function to return the key MONEY-IN

Answer 1

There's zero reason to use Lodash or any other utility library for this.

You can use Array.prototype.find() to find the first object entry (key / value) pair matching your criteria, then return the key for that entry

const obj = {
  'MONEY-OUT': {
    USD: ['a', 'b', 'c'],
    EUR: ['d', 'e', 'f'],
  },
  'MONEY-IN': {
    USD: ['g', 'h', 'i'],
    EUR: ['j', 'k', 'l'],
  },
};

const findKey = (currency, search_string) =>
  Object.entries(obj).find(([, v]) =>
    v[currency]?.includes(search_string),
  )?.[0];

console.log('EUR[k]', findKey('EUR', 'k'));
console.log('USD[b]', findKey('USD', 'b'));
console.log('GBP[z]', findKey('GPB', 'z'));