CODEWITHSUNDEEP
javascriptarraystypescriptobject
user6131384
user6131384

Reputation:

Find continent of each country

I have an array of continents and countries:

const continents = [
  {
    continent: 'Europe',
    countries: [
      'Albania',
      'Andorra',...
    ],
  },
  {
    continent: 'Asia',
    countries: [
      'Afghanistan',
      'Bahrain',...
    ],
  },
  {
    continent: 'Africa',
    countries: [
      'Algeria',
      'Angola',...
    ],
  },
  {
    continent: 'Americas',
    countries: [
      'Antigua and Barbuda',
      'Bahamas',...
    ],
  },
]

And an array of some countries:

const countries = ['Angola', 'Andorra']

I want to iterate over countries and return an array of objects like that:

const result = countries.map(country => {
  return {
    continent: ??,
    country: country,
  }
})

How can I find the continent of each countries?

I try this:

const continent = continents.forEach((continent, i) => {
  const countries = continent.countries
  if (find(countries, value.country)) return continent.continent
})

But I get

[ts] Not all code paths return a value. [7030]

Upvotes: 3

Views: 2367

Answers (5)

Slai
Slai

Reputation: 22876

For multiple lookups, more efficient approach would be to create a lookup object :

const lookup = {}, countries = ['Angola', 'Andorra'], continents = [ { continent: 'Europe', countries: [ 'Albania', 'Andorra' ], }, { continent: 'Asia', countries: [ 'Afghanistan', 'Bahrain' ], }, { continent: 'Africa', countries: [ 'Algeria', 'Angola' ], }, { continent: 'Americas', countries: [ 'Antigua and Barbuda', 'Bahamas' ] } ];

for (let obj of continents)
  for (let country of obj.countries)
     lookup[country] = obj.continent;
 
const result = countries.map(country => ({ country, continent: lookup[country] }));

console.log( result );
console.log( lookup );

Upvotes: 0

anuragb26
anuragb26

Reputation: 1475

First reduce the continents array to an object with key as continent and value as the countries array.

let continentObj = continents.reduce((obj,currentObj) => {
obj[currentObj.continent] = currentObj.countries 
return obj
},{})

Then get the continent by running a map on countries and find the continent inside the object created in the reduce step.

 const countryObj = countries.map(country => {
  const continent = Object.keys(continentObj).find(continentName => continentObj[continentName].indexOf(country) > -1)
 return {
  continent,
  country
}
})
console.log(countryObj)

Upvotes: 0

Code Maniac
Code Maniac

Reputation: 37755

You can use reduce and includes.

So here the idea is loop through the continent array and filter the countries which are available in countries array. Than map through the matchingCountry and create a object with desired keys and push in final output.

const continents = [{ continent:'Europe',countries: ['Albania','Andorra',],},{continent: 'Asia',countries: ['Afghanistan',  'Bahrain', ],  },{continent: 'Africa',countries: ['Algeria',  'Angola',],},{continent: 'Americas',countries: [   'Antigua and Barbuda','Bahamas',],},]

const countries = ['Angola','Andorra', 'Andorra', 'Bahamas']

const output = continents.reduce((op,cur) => {
  let matchCounrty = cur.countries.filter(e =>  countries.includes(e) )
  if( matchCounrty && matchCounrty.length ){
    let desiredObject = matchCounrty.map(e => ({
      continent: cur.continent,
      country: e
    }))
    op.push(desiredObject)
  }
  return op
},[])

console.log(output)

Upvotes: 0

Maheer Ali
Maheer Ali

Reputation: 36584

You need to map map each country name country name to newObj. And then you can use find() method on continents to find out whether the countries array of that continent obj contains the country name or not

const continents = [
  {
    continent: 'Europe',
    countries: [
      'Albania',
      'Andorra'
    ],
  },
  {
    continent: 'Asia',
    countries: [
      'Afghanistan',
      'Bahrain'
    ],
  },
  {
    continent: 'Africa',
    countries: [
      'Algeria',
      'Angola'
    ],
  },
  {
    continent: 'Americas',
    countries: [
      'Antigua and Barbuda',
      'Bahamas'
    ],
  },
]

const countries = ['Angola', 'Andorra']
const result = countries.map(count => {
	const obj = {country:count};
	//get the continent object from array continents which includes 'count' in its countries array
	const continentObj = continents.find(continent=>continent.countries.includes(count));
	//add continent name to the obj as continent name in continentObj
	obj.continent = continentObj.continent;
	return obj;
})
console.log(result);

Upvotes: 0

Nina Scholz
Nina Scholz

Reputation: 386654

You could find continent by checking the value with Array#find and Array#includes

const
    continents = [{ continent: 'Europe', countries: ['Albania', 'Andorra'] }, { continent: 'Asia', countries: ['Afghanistan', 'Bahrain'] }, { continent: 'Africa', countries: ['Algeria', 'Angola'] }, { continent: 'Americas', countries: ['Antigua and Barbuda', 'Bahamas'] }],
    countries = ['Angola', 'Andorra'],
    result = countries.map(country => ({
        continent: continents.find(({ countries }) =>
            countries.includes(country)).continent,
        country,
    }));

console.log(result);

Upvotes: 4

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