World Factbook

Get a button for each letter

• Show a button for each letter that a country can begin with
• You can use a Set to remove duplicates from a list.

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let letters = r.map(c=>c.name[0]);
     for(let a of letters){
       let b = document.createElement('button');
       b.innerText = a;
       document.body.append(b);
     }
  });

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let letters = new Set(r.map(c=>c.name[0]));
     for(let a of letters){
       let b = document.createElement('button');
       b.innerText = a;
       document.body.append(b);
     }
  });

Get a button for each continent

• Show a button for each continent

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let c = [...new Set(r.map(c=>c.continent))];
     c.sort();
     for(let a of c){
       let b = document.createElement('button');
       b.innerText = a;
       document.body.append(b);
     }
  });

Pick a random country from Africa

• Use Math.random() to pick a country at random
• Note that because of the way the scoring works you should not expect to get 100%

The sample code shows a random country beginning with 'A'

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let alist = r.filter(c=>c.name[0]==='A');
     let randomNumber = Math.floor(Math.random()*alist.length);
     let randomCountry = alist[randomNumber];
     document.body.innerText = randomCountry.name;
  });

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let africa = r.filter(c=>c.continent==='Africa');
     let randomNumber = Math.floor(Math.random()*africa.length);
     let randomCountry = africa[randomNumber];
     document.body.innerText = randomCountry.name;
  });

Pick four random countries

• A large country is one with a population of at least 100 million
• Pick four large countries, without repetition

Bangladesh
Brazil
China
India
Indonesia
Japan
Mexico
Nigeria
Pakistan
Russia
United States

• One way to achieve this is to take a copy of the original list then sort it into a random order.
  • You can attach a random number ot each country, then sort by that value.
• You can then take the first four elements of the sorted list.

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let alist = r.filter(c=>c.population >= 100000000);
     for(let c of alist){
       c.rand = Math.random();
     }
     alist.sort((a,b)=>a.rand-b.rand);
     for(let i=0;i<alist.length;i++){
       let d = document.createElement('div');
       d.innerText = alist[i].name;
       document.body.append(d);
     }
  });

fetch('/worldl.json')
  .then((r)=>r.json())
  .then((r)=>{
     let alist = r.filter(c=>c.population >= 100000000);
     for(let c of alist){
       c.rand = Math.random();
     }
     alist.sort((a,b)=>a.rand-b.rand);
     for(let i=0;i<4;i++){
       let d = document.createElement('div');
       d.innerText = alist[i].name;
       document.body.append(d);
     }
  });