const square = x => x * x;
const add = (x, y) =>x + y;
const log = result => {
    console.log(result);
    return result;
};
const result = log(square(add(3,5)));
//  yields 64
///////////////////////// ok
const numbers = [1,2,3];
const result = numbers.map(n => n * 2);
// [2,4,6]
///////////////////////// bad
const numbers = [1,2,3];
const result = numbers.map(n => { value: n});
// [undefined], [undefined], [undefined]  //BAD !!!!
///// /////////////////// SOLUTION
const numbers = [1,2,3];
const result = numbers.map(n => ({ value: n}));
// [{value:1},{value:2},{value:3}]