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JavaScript JavaScript Array Iteration Methods Combining Array Methods Nested Data

Posted by Lisa Carbonell
.a{fill-rule:evenodd;}techdegree seal-36
Lisa Carbonell
Full Stack JavaScript Techdegree Graduate 16,926 Points

Confused...

hobbies = customers .map(customer => customer.personal.hobbies.map(hobby => hobby)) .reduce((arr, cur) => [...arr, ...cur.personal.hobbies], []);

console.log(hobbies);

app.js 
const customers = [
  {
    name: "Tyrone",
    personal: {
      age: 33,
      hobbies: ["Bicycling", "Camping"]
    }
  },
  {
    name: "Elizabeth",
    personal: {
      age: 25,
      hobbies: ["Guitar", "Reading", "Gardening"]
    }
  },
  {
    name: "Penny",
    personal: {
      age: 36,
      hobbies: ["Comics", "Chess", "Legos"]
    }
  }
];
let hobbies;

// hobbies should be: ["Bicycling", "Camping", "Guitar", "Reading", "Gardening", "Comics", "Chess", "Legos"]
// Write your code below

hobbies = customers
    .map(customer => customer.personal.hobbies.map(hobby => hobby))
    .reduce((arr, cur) => [...arr, ...cur.personal.hobbies], []);

console.log(hobbies);

2 Answers

Steven Parker
Steven Parker
231,521 Points
Steven Parker
Steven Parker
231,521 Points

You're working too hard — you don't need "map" for this challenge. In fact, you've done such a great job with the "reduce" function that if you just remove the "map" line completely you will pass the challenge. :wink:

Happy coding!

Ross King
Ross King
20,704 Points
Ross King
Ross King
20,704 Points

Hi Lisa Carbonell ,

Steven Parker is correct and it will give you the best result by removing the map function. I wanted to let you know why you're code is resulting in an error (or challenge fail).

.map is returning an array of hobbies e.g. ["Bicycling", "Camping", "Guitar", ...rest] .reduce is trying to access an array item with the properties of personal.hobbies, however this is undefined as you have just converted the array into strings instead of objects.

For your code to with a map function, the following example will work.

hobbies = customers
    .map(customer => customer.personal.hobbies)
    .reduce((arr, cur) => [...arr, ...cur], []);

As Steven answered previously, the following is the best way to solve this challenge:

hobbies = customers
    .reduce((arr, cur) => [...arr, ...cur.personal.hobbies], []);