How to apply properties of an object to functions?

Question

I want to apply different functions to some object properties. Lets say I have this object:

const person = {
  name: 'John',
  age: 30,
  friends: [],
};

and i have some functions that i want to apply to those properties:

const upperCase = str => str.toUpperCase() //for the name

const add10 = int => int + 10 // for the age

const addFriend = (value,list) => [...list,value] // adding a friend

and this should be the result:

const person = {
  name: 'JOHN',
  age: 40,
  friends: ['Lucas']
}

What is the best way to achieve this using functional programming and point free, and if you could include examples using Ramda I would appreciate it, Thanks!

Answer 1

With Ramda, you're looking at the evolve function:

Creates a new object by recursively evolving a shallow copy of object, according to the transformation functions. All non-primitive properties are copied by reference.

You probably need to define "transform" functions on the fly; I bet you don't want to add 'Lucas' as a friend of every single person. Hopefully this is enough to get you started.

const transform =
  evolve(
    { name: toUpper
    , age: add(10)
    , friends: prepend('Lucas')
    });
    
    
console.log(

  transform(person)

);

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>
<script>const {evolve, toUpper, add, prepend} = R;</script>
<script>
const person =
  { name: 'John'
  , age: 30
  , friends: []
  };
</script>

---

Point-free style is not the only way

⚠️

Please note that I've been able to implement this point-free style because I could hardcode each transformation functions. If you need to craft a transformation object on the fly, doing so point-free style is likely to be unreadable quickly.