example.ts

import { INutritionData } from '../models/nutrition-data.interface';
import { Ingredient } from '../models/ingredient';
import { RecipeIngredient } from '../models/recipe-ingredient';
import * as _ from 'lodash';

export class NutritionCalculatorService {
  public calculate(ingredients: RecipeIngredient[]): INutritionData {
    const result = new Ingredient(null, null);

    const properties = ['calories', 'sodium'];

    _.each(ingredients, (i): void => {
      _.each(properties, (p): void => {
        this.add(result, i, p);
      });
    });

    return result;
  }

  private add(runningTotal: INutritionData, addition: RecipeIngredient, property: string): void {
    runningTotal[property] += addition.quantity * addition[property];
  }
}