How to return more than one thing using map()

Tell us what’s happening:
I’m trying to use the map() method to extract data from an array. Following the example given I can pass one item from the list. For instance we have a list of movies. I know how to get the rating for each movie from the list using map. But I dont know the syntax for getting more than one thing, for instance rating and title.

Your code so far

// The global variable
const watchList = [
  {
    "Title": "Inception",
    "Year": "2010",
    "Rated": "PG-13",
    "Released": "16 Jul 2010",
    "Runtime": "148 min",
    "Genre": "Action, Adventure, Crime",
    "Director": "Christopher Nolan",
    "Writer": "Christopher Nolan",
    "Actors": "Leonardo DiCaprio, Joseph Gordon-Levitt, Elliot Page, Tom Hardy",
    "Plot": "A thief, who steals corporate secrets through use of dream-sharing technology, is given the inverse task of planting an idea into the mind of a CEO.",
    "Language": "English, Japanese, French",
    "Country": "USA, UK",
    "Awards": "Won 4 Oscars. Another 143 wins & 198 nominations.",
    "Poster": "http://ia.media-imdb.com/images/M/MV5BMjAxMzY3NjcxNF5BMl5BanBnXkFtZTcwNTI5OTM0Mw@@._V1_SX300.jpg",
    "Metascore": "74",
    "imdbRating": "8.8",
    "imdbVotes": "1,446,708",
    "imdbID": "tt1375666",
    "Type": "movie",
    "Response": "True"
  },
  {
    "Title": "Interstellar",
    "Year": "2014",
    "Rated": "PG-13",
    "Released": "07 Nov 2014",
    "Runtime": "169 min",
    "Genre": "Adventure, Drama, Sci-Fi",
    "Director": "Christopher Nolan",
    "Writer": "Jonathan Nolan, Christopher Nolan",
    "Actors": "Ellen Burstyn, Matthew McConaughey, Mackenzie Foy, John Lithgow",
    "Plot": "A team of explorers travel through a wormhole in space in an attempt to ensure humanity's survival.",
    "Language": "English",
    "Country": "USA, UK",
    "Awards": "Won 1 Oscar. Another 39 wins & 132 nominations.",
    "Poster": "http://ia.media-imdb.com/images/M/MV5BMjIxNTU4MzY4MF5BMl5BanBnXkFtZTgwMzM4ODI3MjE@._V1_SX300.jpg",
    "Metascore": "74",
    "imdbRating": "8.6",
    "imdbVotes": "910,366",
    "imdbID": "tt0816692",
    "Type": "movie",
    "Response": "True"
  },
  {
    "Title": "The Dark Knight",
    "Year": "2008",
    "Rated": "PG-13",
    "Released": "18 Jul 2008",
    "Runtime": "152 min",
    "Genre": "Action, Adventure, Crime",
    "Director": "Christopher Nolan",
    "Writer": "Jonathan Nolan (screenplay), Christopher Nolan (screenplay), Christopher Nolan (story), David S. Goyer (story), Bob Kane (characters)",
    "Actors": "Christian Bale, Heath Ledger, Aaron Eckhart, Michael Caine",
    "Plot": "When the menace known as the Joker wreaks havoc and chaos on the people of Gotham, the caped crusader must come to terms with one of the greatest psychological tests of his ability to fight injustice.",
    "Language": "English, Mandarin",
    "Country": "USA, UK",
    "Awards": "Won 2 Oscars. Another 146 wins & 142 nominations.",
    "Poster": "http://ia.media-imdb.com/images/M/MV5BMTMxNTMwODM0NF5BMl5BanBnXkFtZTcwODAyMTk2Mw@@._V1_SX300.jpg",
    "Metascore": "82",
    "imdbRating": "9.0",
    "imdbVotes": "1,652,832",
    "imdbID": "tt0468569",
    "Type": "movie",
    "Response": "True"
  },
  {
    "Title": "Batman Begins",
    "Year": "2005",
    "Rated": "PG-13",
    "Released": "15 Jun 2005",
    "Runtime": "140 min",
    "Genre": "Action, Adventure",
    "Director": "Christopher Nolan",
    "Writer": "Bob Kane (characters), David S. Goyer (story), Christopher Nolan (screenplay), David S. Goyer (screenplay)",
    "Actors": "Christian Bale, Michael Caine, Liam Neeson, Katie Holmes",
    "Plot": "After training with his mentor, Batman begins his fight to free crime-ridden Gotham City from the corruption that Scarecrow and the League of Shadows have cast upon it.",
    "Language": "English, Urdu, Mandarin",
    "Country": "USA, UK",
    "Awards": "Nominated for 1 Oscar. Another 15 wins & 66 nominations.",
    "Poster": "http://ia.media-imdb.com/images/M/MV5BNTM3OTc0MzM2OV5BMl5BanBnXkFtZTYwNzUwMTI3._V1_SX300.jpg",
    "Metascore": "70",
    "imdbRating": "8.3",
    "imdbVotes": "972,584",
    "imdbID": "tt0372784",
    "Type": "movie",
    "Response": "True"
  },
  {
    "Title": "Avatar",
    "Year": "2009",
    "Rated": "PG-13",
    "Released": "18 Dec 2009",
    "Runtime": "162 min",
    "Genre": "Action, Adventure, Fantasy",
    "Director": "James Cameron",
    "Writer": "James Cameron",
    "Actors": "Sam Worthington, Zoe Saldana, Sigourney Weaver, Stephen Lang",
    "Plot": "A paraplegic marine dispatched to the moon Pandora on a unique mission becomes torn between following his orders and protecting the world he feels is his home.",
    "Language": "English, Spanish",
    "Country": "USA, UK",
    "Awards": "Won 3 Oscars. Another 80 wins & 121 nominations.",
    "Poster": "http://ia.media-imdb.com/images/M/MV5BMTYwOTEwNjAzMl5BMl5BanBnXkFtZTcwODc5MTUwMw@@._V1_SX300.jpg",
    "Metascore": "83",
    "imdbRating": "7.9",
    "imdbVotes": "876,575",
    "imdbID": "tt0499549",
    "Type": "movie",
    "Response": "True"
  }
];

// Only change code below this line

const ratings = watchList.map( watchList => watchList.imdbRating, watchList.Title);


// Only change code above this line

console.log(JSON.stringify(ratings));

Your browser information:

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Challenge: Use the map Method to Extract Data from an Array

Link to the challenge:

Hello there.

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If so, please edit your post to include it in the Tell us what’s happening section.

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1 Like

What kind of data structures in JS would allow you to return multiple values? Obviously something like a string or number won’t let you do it because those can only hold a single value. Remember, map is just going through the array and returning a new array. What type of values does the array contain? That should be a clue as to what type of value you should return in the callback to map.

You’re trying to get an object returned for each movie in the array, with the object containing the movies title and IMDB rating. Try changing your code to having the .map function return an object with two properties (title and rating).

The syntax would look like this:

// array of data
const people = [
{ name: "eesa", age: 20 , codingLanguage: "Javascript"},
{ name: "bob", age: 21, codingLanguage: "Python" },
]

// mapping through every object in the array and returning just the name and age
const nameAndAge = people.map(person => ({
    name: person.name,
    age: person.age
}));

console.log(JSON.stringify(nameAndAge));
// [{"name":"eesa","age":20},{"name":"bob","age":21}]
1 Like

Ok something I don’t understand. The variable person isn’t declared anywhere. Like let person = . The first time it appears is when you call map. So when you call map you have to create a new variable?

Ahh, but it is. Remember, you are passing a function into map() and then map applies that function to each item in the array. You can declare parameters for functions, such as:

function callback(person) {
  ...
}

And when you call the function you can pass an argument into it and it will be stored in person inside the function. You are doing the same thing with map, you are passing a callback function into map with one parameter defined. As map iterates through the array it automatically passes each item in the array into your callback function, and so person takes on the value of the item.

3 Likes

Basically, I defined person as an identifier for each object in the array. Imagine it like this.

const nameAndAge = people.map(person => ({ 
    /* for every person in people, create a new object 
       with individual properties. So for the first iteration, 
       person is equal to people[0] (Eesa), and for the 
       second iteration, person is equal to people[1] (Bob) */
    name: person.name,
    age: person.age
}));

console.log(JSON.stringify(nameAndAge));
/* for the new array that was mapped, it has two new objects, 
but they contains parts of the old array. */
1 Like

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