Write code for humans!

Not for machines

Humans prefer this

Functional programming

            const kmOfItalianDrivers = users
              .filter(u => u.country === 'ITALY' && 
                           u.hasDriverLicence &&
                           u.age >= 18
              .flatMap(u => u.cars)
              .reduce((totalKm, car) => totalKm + car.km, 0);

Machines prefer this

Imperative code

              let kmOfItalianDrivers = 0;

              for (let i = 0; i < users.length; i++) {
                if (users[i].country === 'ITALY' &&
                    users[i].hasDriverLicence &&
                    users[i].age >= 18) {
                      for (let j = 0; j < users[i].cars.length; j++) {
                        kmOfItalianDrivers += users[i].cars[j].km;
              return kmOfItalianDrivers;

Why humans prefer
functional programming

  • It focuses on what you want to achieve
  • Fewer lines of code
  • It encourages code reusability (composing map, flatMap, filter, reduce etc.)
  • It hides implementation details

Why machines prefer
imperative programming

  • It focuses on how you want to achieve it
  • You write what the machine should do
  • Better performance (not always)

When you write code

  • Someone will review it
  • Someone should be able to understand it
  • Someone will take inspiration from that
  • Someone will build on top of it

Hardware is cheap,
developers are expensive

  • It's better to save hours spent by developers instead of milliseconds spent by machines
  • You should help your team building things quickly

So write human-friendly code

  • Functional programming can help you
  • Your code will be easier to understand and easier to change
  • Your colleagues will appreciate!

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