Practice Exercise #16

Javascript Programming
#1

Hello I’m brand new to JavaScript and I’ve been working through the course and the exercises.
On exercise 16:

  1. Write a script, the script should calculate the total price for a user after a shopping trip.
  2. The items that can be bought are bread, milk, cheese, and yogurt.

The prices are as follows:

Bread: € 2.

Milk: € 1.5.

Cheese: € 4.

Yogurt: € 1.2.

I used the following asnwer:

var bread = "2";
var milk = "1.5";
var cheese = "4";
var yogurt = "1.2";
alert("Hi! Welcome to the Ivan on Tech Shop!");
var qtyBread = prompt("How much bread do you want?");
var qtyMilk = prompt("How much milk do you want?");
var qtyCheese = prompt("How much cheese do you want?");
var qtyYogurt = prompt("How much Yogurt do you want?");
var total = (bread*qtyBread + milk*qtyMilk + cheese*qtyCheese + yogurt*qtyYogurt);
console.log("The total amount to pay is", total);

The code works fine and gives the correct solution however, I noticed my answer was very different from the one given in the solution. Which is:

var​ bread = ​2​;
var​ milk = ​1.5​;
var​ cheese = ​4​;
var​ yogurt = ​1.2​;

var​ sum = ​0​;

alert(​"Hi! Welcome to the Ivan on Tech Shop!"​);

var​ input = prompt(​"How much bread do you want?"​);
sum += input * bread;
var​ input = prompt(​"How much milk (liter) do you want?"​);
sum += input * milk;
var​ input = prompt(​"How much cheese do you want"​);
sum += input * cheese;
var​ input = prompt(​"How many yogurts do you want?"​);
sum += input * yogurt;

console​.log(​"The total amount to pay is"​, sum);

I was just wondering if anyone knew if it is better practice to define a variable, in this case sum as 0 and use that as a sort of running total if so why?

#2

Hi,

I believe your initial answer for calculating the total only at the end is more efficient. It has lesser computations thus it does not take as many resources and time.

Coming to the sum variable declaration, yes it is a good practise to define the initial value of a variable before using it, in case issues arise, you do not want the implicit value to be your fallback answer. It is always a good practice defining the initial value of a variable.

Another point to note, your initial value declarations of bread, milk prices are in strings. Since you will be performing arithmetic, you should make sure to make it a number. Here, your javascript implicitly converted the string into numbers and did the calculations. But you do not want to rely on implicit conversions as it might cause issues when your code becomes more complex.

Hope this helps. :slight_smile:\

Happy coding!

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#3

Hi Malik,

That makes a lot of sense. Thank you for clearing that up for me :grinning:

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