findKey.js

// FUNCTION IMPLEMENTATION
// returns the key of the first element predicate returns truthy for
const findKey = function(object, callback) {
  for (let key in object) {
    if (callback(object[key])) {
      return key;
    }
  }
  return 'No Key with this value'
}

module.exports = findKey;

/* Test Code
const assertEqual = function(actual, expected) {
  if (actual === expected) {
    console.log(`✅✅✅ Assertion Passed: '${actual}' === '${expected}'`);
  } else {
    console.log(`🛑🛑🛑 Assertion Failed: '${actual}' !== '${expected}'`);
  }
};

test1 = findKey({
  "Blue Hill": { stars: 1 },
  "Akaleri":   { stars: 3 },
  "noma":      { stars: 2 },
  "elBulli":   { stars: 3 },
  "Ora":       { stars: 2 },
  "Akelarre":  { stars: 3 }
}, x => x.stars === 2) // => "noma"

assertEqual(test1, 'noma');

test2 = findKey({
  "Blue Hill": { stars: 1 },
  "Akaleri":   { stars: 3 },
  "noma":      { stars: 2 },
  "elBulli":   { stars: 3 },
  "Ora":       { stars: 2 },
  "Akelarre":  { stars: 3 }
}, x => x.stars === 4) // => "No Key with this value"
assertEqual(test2, 'No Key with this value');
*/