Currying and Decorator examples

by: Grecia

What is CurrYing

A curried function is a function that takes multiple arguments one at a time.

what is closure

A closure gives you access to an outer function’s scope from an inner function. In JavaScript, closures are created every time a function is created, at function creation time.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures

https://medium.com/javascript-scene/curry-and-function-composition-2c208d774983

this is a closure

this function refers to the closure above

// Normal Function 
function sum(a,b,c){
  return a+b+c
}

//Function with clousure
function sum(a){
  return function(b){
    return function(c){
      return a+b+c
    }
  }
}

//Function with clousure with arrow function
let currySum = (a)=>(b)=>(c)=> a+b+c;


// Normal console.log of a function
console.log(sum(1,2,3)) // 6

// console.log of a Function with a clousure
let sumWithClousure= currySum(1)(2)(3)
console.log(sumWithClousure)

function discount(discount, price) {
  return discount*price
}

const discount10per = discount(0.1,500);
const discount20per = discount(0.2,500);
const discount30per = discount(0.3,500);
const discount40per = discount(0.4,500);
const discount50per = discount(0.5,500);

console.log(discount10per)
console.log(discount20per)
console.log(discount30per)
console.log(discount40per)
console.log(discount50per)

function discount(discount){
  return function(price){
    return price*discount
  }
}

let discount10per= discount(0.1)
let discount20per= discount(0.2)
let discount30per= discount(0.3)
let discount40per= discount(0.4)
let discount50per= discount(0.5)

console.log(discount10per(500))
console.log(discount20per(500))
console.log(discount30per(500))
console.log(discount40per(500))
console.log(discount50per(500))

CurRyng and inheritance

const createPerson = (type)=>{
  let person={
    name:'Person',
    age: 0,
    isWoman: true,
    type:type
  };

  return (name, age , isWoman)=>{
      person.name = name || person.name
      person.age = age || person.age
      person.isWoman = isWoman 
      return person
  }
}

let createaMom = createPerson('Mom')('Carmen',45,true)
console.log(createaMom)

let createaDad = createPerson('Dad')('Mauricio',53,false)
console.log(createaDad)

//{ name: 'Carmen', age: 45, isWoman: true, type: 'Mom' }
//{ name: 'Mauricio', age: 53, isWoman: false, type: 'Dad' }

Conclusions

Closure makes currying possible in JavaScript
It’s ability to retain the state of functions already executed, gives us the ability to create factory🏭

DEcorators

What is decorator

A decorator is simply a way of wrapping a function with another function to extend its existing capabilities. You “decorate” your existing code by wrapping it with another piece of code

https://dev.to/anuradha9712/call-apply-bind-methods-in-javascript-4pfn

let person = {
  name: 'Grecia',
  sayName(age, city, pet) {
   return console.log(`Hi, ${this.name}. You are ${age} and live in ${city} and you have a ${pet}`)
 }
}

function decorator(fn, context) {
  let count = 0;
  return function(...args) {
  count ++;
  console.log(`Function ${fn.name} has been called ${count} time(s)`)
  return fn.call(context, ...args)
 }
}

decorator(person.sayName, person)(22, 'Lima','parrot')

Thanks!

Currying and Decoratos

By Grecia Delgado