const scores = [45, 72, 88, 39, 91, 66];

// map: a new array, one result per item
const percentages = scores.map(score => score + '%');
console.log('As percentages:', percentages);

// filter: only the items that pass a test
const passed = scores.filter(score => score >= 50);
console.log('Passed (50 and above):', passed);

// reduce: combine everything into one value
const total = scores.reduce((sum, score) => sum + score, 0);
console.log('Average score:', (total / scores.length).toFixed(1));