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JavaScript JavaScript Array Iteration Methods Combining Array Methods Nested Data

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,253 Points

Okay, one more time....

Okay....

I seem to have successfully flattened the array but they're all coming up undefined. I've been at this for an hour (I can be quite stubborn)

I'm trying to access the nested hobbies property. What am I getting wrong? Thanks :)

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

  console.log(hobbies);

2 Answers

Hey man, I got it working using a single .map() and the .concat() method inside the .reduce().

hobbies = customers
.map(customer => customer.personal.hobbies)
.reduce((mainArr, customerArr) => mainArr.concat( customerArr ), []);
Charles Tinley
Charles Tinley
8,012 Points

hobbies= customers .map(customer => customer.personal.hobbies) .reduce((mainArr, customerArr)=> [...mainArr, ...customerArr], []);