How can I sum numbers which are substrings in variables?

November 8, 2021

I was wondering how can you combine two variables (or more) that have the same string values, but different numbers.

For example, if you’re combining a list of ingredients that are present in two different recipes. For a shopping list, like:

let ingredient1 = 1 + " apple";
let ingredient2 = 2 + " apple";
//combining ingredient1 and ingredient 2 would produce something like totalIngredients = 3 apples;

I can kind of figure out the pluralization, but I can’t figure out how I can combine those two strings and for it to only increase the number if they’re matching.

>Solution :

Like others have noted, you should store your ingredients as objects. One way to achieve this is to have a class which stores the count and ingredient type. You can then define a function that checks for a given type and returns the count of ingredients.

class Ingredient {  
  constructor(count, type) {
    this.count = count;
    this.type = type;
  }
};

const countByType = (type) => ingredients.reduce((sum, ingredient) => {
  if (ingredient.type === type) {
    return sum += ingredient.count;
  }

  return sum;
}, 0);

const ingredients = [];
ingredients.push(new Ingredient(1, "apple"));
ingredients.push(new Ingredient(2, "apple"));
ingredients.push(new Ingredient(5, "orange"));



console.log(`${countByType("apple")} apples`);
console.log(`${countByType("orange")} oranges`);

If you prefer, you can achieve the same without classes as well:

const countByType = (type) => ingredients.reduce((sum, ingredient) => {
  if (ingredient.type === type) {
    return sum += ingredient.count;
  }

  return sum;
}, 0);

const ingredients = [];
ingredients.push({count: 1, type: "apple"});
ingredients.push({count: 2, type: "apple"});
ingredients.push({count: 5, type: "orange"});



console.log(`${countByType("apple")} apples`);
console.log(`${countByType("orange")} oranges`);