@kowo0403hk/lotide/findKey.js

lotide library by LHL Bootcamp student

// Implement the function findKey which takes in an object and a callback. It should scan the object and return the first key for which the callback returns a truthy value. If no key is found, then it should return undefined.

const assertEqual = function(actual, expected) {
  if (actual === expected) {
    console.log(`\u2705\u2705\u2705 Assertion Passed: ${actual} === ${expected}`);
  } else {
    console.log(`\u26d4\u26d4\u26d4 Assertion Failed: ${actual} !== ${expected}`);
  }
};

const findKey = (obj, callback)  => {
  for (let key in obj) {
    if (callback(obj[key])) return key;
  }
  return undefined;
};


// test case
console.log(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(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(findKey({
  "Surrey":     { expLevel: 3},
  "Delta":      { expLevel: 5},
  "Vancouver":  { expLevel: 9},
  "Burnaby":    { expLevel: 7},
}, x => x.expLevel === 9), "Vancouver");