helpTheBookseller.js

// A bookseller has lots of books classified in 26 categories labeled A, B, ... Z. Each book has a code c of 3, 4, 5 or more characters. The 1st character of a code is a capital letter which defines the book category.

// In the bookseller's stocklist each code c is followed by a space and by a positive integer n (int n >= 0) which indicates the quantity of books of this code in stock.

// For example an extract of a stocklist could be:

// L = {"ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"}.
// or
// L = ["ABART 20", "CDXEF 50", "BKWRK 25", "BTSQZ 89", "DRTYM 60"] or ....
// You will be given a stocklist (e.g. : L) and a list of categories in capital letters e.g :

// M = {"A", "B", "C", "W"} 
// or
// M = ["A", "B", "C", "W"] or ...
// and your task is to find all the books of L with codes belonging to each category of M and to sum their quantity according to each category.

// For the lists L and M of example you have to return the string (in Haskell/Clojure/Racket a list of pairs):

// (A : 20) - (B : 114) - (C : 50) - (W : 0)
// where A, B, C, W are the categories, 20 is the sum of the unique book of category A, 114 the sum corresponding to "BKWRK" and "BTSQZ", 50 corresponding to "CDXEF" and 0 to category 'W' since there are no code beginning with W.

// If L or M are empty return string is "" (Clojure and Racket should return an empty array/list instead).

// my original solution

function stockList(listOfArt, listOfCat){
    if(!listOfArt.length) return ''
    let result = []
    let stock = listOfCat.reduce((a,b)=> {
      if(!a[b]) {
        a[b] = 0
      }
      return a
    }, {})
  
    listOfArt.forEach(a => {
      if(a[0] in stock){
        stock[a[0]] += Number(a.split(" ")[1])
      }
    })
    
    for(const key in stock) {
      result.push(`(${key} : ${stock[key]})`)
    }
    
    return result.join(' - ')
}