Hello world!

const beatles = [
   { 
     name: 'John'
     instrument: 'guitar',
     status: 'dead'
   },
   {
     name: 'Paul',
     instrument: 'bass',
     status: 'living'
   },
   {
     name: 'George',
     instrument: 'guitar',
     status: 'dead'
   },
   {
     name: 'Ringo',
     instrument: 'drums',
     status: 'living'
   },
 ];

How many members of The Beatles are living?

const isLiving = function(beatle) {
   return beatle.status == 'living';
 }
 const livingBeatles = beatles.filter(isLiving).length;
 console.log(livingBeatles); // 2

Are there any living members of The Beatles that play drums?

const isLivingAndDrummer = function(beatle) {
   return beatle.status == 'living' && beatle.instrument == 'drums';
 }
 const livingBeatleDrummers = beatles.some(isLivingAndDrummer);
 console.log(livingBeatleDrummers); // true

Which members of The Beatles played stringed instruments?

const hasStringedInstrument = function(accumulator, beatle) {
   if (beatle.instrument == 'guitar' || beatle.instrument == 'bass') {
     return accumulator = […accumulator, beatle.name];
   } else {
     return accumulator;
   }
 }
 const playedStringed = beatles.reduce(hasStringedInstrument, []);
 console.log(playedStringed); // ['John', 'Paul', 'George']
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