I currently have an array that looks like this:

var array = [
  {
    "title": "Ender's Game",
    "genre": "Science Fiction",
    "year": 2008
  },
  {
    "title": "Harry Potter and the Goblet of Fire",
    "genre": "fantasy",
    "year": 2002
  },
  {
    "title": "Pride and Predjudice",
    "genre": "romance",
    "year": 1980
  }
]

I want to iterate through this array and find the length of the longest genre. I want something like this:

longestGenre(array);
15

Ive tried a few things including the following:

var getLongest = (array, key) =>
{
  let r = Object.values(array).reduce((res, curr) =>
  {
      if (!Array.isArray(curr))
          return res;

      let newMax = curr.reduce(
          (r, c) => c[[key]] && (c[[key]].length > r.length) ? c[[key]] : r,
          ""
      );

      res = newMax.length > res.length ? newMax : res;
      return res;

  }, "");
  longest = r;
  return longest;
}

And another approach I tried was this:

  for (key in obj){
      if (!obj.hasOwnProperty(key)) continue;
          if (obj.key.length > longest)
              longest = obj.key.length;
  }

I currently have an array that looks like this:

var array = [
  {
    "title": "Ender's Game",
    "genre": "Science Fiction",
    "year": 2008
  },
  {
    "title": "Harry Potter and the Goblet of Fire",
    "genre": "fantasy",
    "year": 2002
  },
  {
    "title": "Pride and Predjudice",
    "genre": "romance",
    "year": 1980
  }
]

I want to iterate through this array and find the length of the longest genre. I want something like this:

longestGenre(array);
15

Ive tried a few things including the following:

var getLongest = (array, key) =>
{
  let r = Object.values(array).reduce((res, curr) =>
  {
      if (!Array.isArray(curr))
          return res;

      let newMax = curr.reduce(
          (r, c) => c[[key]] && (c[[key]].length > r.length) ? c[[key]] : r,
          ""
      );

      res = newMax.length > res.length ? newMax : res;
      return res;

  }, "");
  longest = r;
  return longest;
}

And another approach I tried was this:

  for (key in obj){
      if (!obj.hasOwnProperty(key)) continue;
          if (obj.key.length > longest)
              longest = obj.key.length;
  }

• javascript

3 Answers 3

You don't need all those checks and nested loops, just map the array to the length of the genre, then take the maximum:

 const longestGenre = Math.max(...array.map(movie => movie.genre.length));

Or dynamically:

const longest = (key, array) => Math.max(...array.map(it => it[key].length));

console.log(longest("genre", /*in*/ array));

You can also use reduce in a cleaner and more pact way.

Working snippet:

var arr = [
  {
    "title": "Ender's Game",
    "genre": "Science Fiction",
    "year": 2008
  },
  {
    "title": "Harry Potter and the Goblet of Fire",
    "genre": "fantasy",
    "year": 2002
  },
  {
    "title": "Pride and Predjudice",
    "genre": "romance",
    "year": 1980
  },
  {
    "title": "Pride and Predjudice",
    "genre": "asdasdasd asdasdasdsa asdasda",
    "year": 1980
  }
]
var longest = arr.reduce(function (a, b) { return a.genre.length > b.genre.length ? a : b; }).genre.length;
console.log(longest); 

You could also sort the array of object lengths in decreasing order of length of genre. Then return the first index of the array which will always hold the greatest length.

var array = [{"title":"Ender's Game","genre":"Science Fiction","year":2008},{"title":"Harry Potter and the Goblet of Fire","genre":"fantasy","year":2002},{"title":"Pride and Predjudice","genre":"romance","year":1980}]
function getLongest(array){
  return array.map((obj) => obj.genre.length).sort((a, b)=>{
         return (b - a); //sorting in descending order
 })[0]; //first element will hold the longest genre
}
console.log(getLongest(array));