Push value of key from array to another array in a for loop JavaScript

Question

I am trying to push a value from a key that exists in the first array. This array consists of a country_users array that I have looped through every users array within this one and pushed these to a new array called users

In this demo I am trying to push country from country_users to every user object in the users array.

I am using Vue.js for this purpose, it might be easier with Vue? Any suggestions?

var users = [];
var country_users = [
  {
    "country": "United States",
    "users": [
      {
        "name": "John"
      },
      {
        "name": "Jane"
      },
    ],
  },
  
  {
    "country": "Norway",
    "users": [
      {
        "name": "Ola"
      },
      {
        "name": "Jens"
      },
    ],
  },
  
];

// Here I push all users from country_users into a new array called users
for (let cu = 0; cu < country_users.length; cu++) {
  for (let u = 0; u < country_users[cu].users.length; u++) {
  users.push(country_users[cu].users[u]);
  }
  
  // Do I make a new for loop here to push the country into every object inside users array? How?
}

console.log(users);

I want to push the country from the array where the users belonged previously.

The result I want is an array like this for users

var users = [
 {
"name": "John",
"country": "United States"
  },
  {
"name": "Jane",
"country": "United States"
  },
  {
"name": "Ola",
"country": "Norway"
  },
  {
"name": "Jens",
"country": "Norway"
  }
];

console.log(users);

SOLUTION

var users = [];
var country_users = [
  {
    "country": "United States",
    "users": [
      {
        "name": "John"
      },
      {
        "name": "Jane"
      },
    ],
  },
  
  {
    "country": "Norway",
    "users": [
      {
        "name": "Ola"
      },
      {
        "name": "Jens"
      },
    ],
  },
  
];

country_users.forEach((country_user) => {
  country_user.users.forEach((user) => {
     user.country = country_user.country;
     users.push(user);
  });
});

console.log(users);

why john not jane and jens not ola? if the first, then ola instead of jens ...? — Nina Scholz
– Nina Scholz, Commented Jan 17, 2018 at 14:19
@NinaScholz Sorry, my bad. I wanted the same result for all users in country_users array. — Pinch
– Pinch, Commented Jan 17, 2018 at 14:41

Nina Scholz · Accepted Answer · 2018-01-17 14:25:22Z

You could iterate the given array and their user array and build a new array with the wanted properties.

var country_users = [{ country: "United States", users: [{ name: "John" }, { name: "Jane" }] }, { country: "Norway", users: [{ name: "Ola" }, { name: "Jens" }] }],
    users = country_users.reduce(function (r, country) {
        country.users.forEach(function (user) {
            r.push({ name: user.name, country: country.country });
        });
        return r;
    }, []);
    
console.log(users);

.as-console-wrapper { max-height: 100% !important; top: 0; }

ES6

var country_users = [{ country: "United States", users: [{ name: "John" }, { name: "Jane" }] }, { country: "Norway", users: [{ name: "Ola" }, { name: "Jens" }] }],
    users = country_users.reduce((r, { country, users }) => {
        users.forEach(({ name }) => r.push({ name, country }));
        return r;
    }, []);
    
console.log(users);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Hemerson Carlin · Accepted Answer · 2018-01-17 14:24:48Z

0

You can use Array.prototype.reduce and in each iteration, you create and return the new array with users and countries:

const country_users = [
  {
    "country": "United States",
    "users": [
      {
        "name": "John"
      },
      {
        "name": "Jane"
      },
    ],
  }, 
  {
    "country": "Norway",
    "users": [
      {
        "name": "Ola"
      },
      {
        "name": "Jens"
      },
    ],
  },  
];

const result = country_users.reduce((prev, curr) => {
  const users = curr.users.map(user => ({
    name: user.name,
    country: curr.country
  }))
  
  return [
    ...prev,
    ...users,
  ]
}, [])

console.log(result)

answered Jan 17, 2018 at 14:24

Hemerson Carlin

7,4241 gold badge29 silver badges38 bronze badges

Comments

Faly · Accepted Answer · 2018-01-17 14:24:52Z

Just add the property country before pushing

var users = [];
var country_users = [
  {
    "country": "United States",
    "users": [
      {
        "name": "John"
      },
      {
        "name": "Jane"
      },
    ],
  },
  
  {
    "country": "Norway",
    "users": [
      {
        "name": "Ola"
      },
      {
        "name": "Jens"
      },
    ],
  },
  
];

// Here I push all users from country_users into a new array called users
for (let cu = 0; cu < country_users.length; cu++) {
  for (let u = 0; u < country_users[cu].users.length; u++) {
     var newUser = country_users[cu].users[u];
     newUser.country = country_users[cu].country;
     users.push(newUser);
  }
  
  // Do I make a new for loop here to push the country into every object inside users array? How?
}

console.log(users);

MathKimRobin · Accepted Answer · 2018-01-17 14:26:38Z

0

Suggest you to use an ES6 syntax :

for(const country of country_users) {
  for(const user of country.users) {
    users.push({
      ...user,
      country : country.country
    })
  }
}

the user object is copied by using rest operator "..."

answered Jan 17, 2018 at 14:26

MathKimRobin

1,5905 gold badges27 silver badges60 bronze badges

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