I need help with this I don't even think it is right as I have a hard time understanding loops. I was asked to create a Javascript Program that asks for any amount and outputs the number of ice candies that can be bought, and the change if any. My problem is that I do not know if "while" is the correct thing to put or "do" or if I'm missing something Thank you in advance. Here is my code

function minitask() {
  var m = document.getElementById("money").value;
  var c = 8.5;

  m = m - c;
  c = c   1;

  while (m <= c)
    alert("You can buy "   c   " Icecandy and your change is "   m);
}

<input type="text" id="money" name= "Enter any amount">
<button onclick="minitask()">Calculate</button>

CodePudding user response：

There are some issues in your code both from a algorithmic point of view and a software design point of view.

Algorithmic

There is no need to use a loop here, you can do a simple division which will give you the number of candies you can buy:

available money / price for one candy = number of candies to buy

You need to floor() the result as you cannot buy e.g. 1.2 candys.

The change can then be calculated by

change = available money - number of candies to buy * price of one candy 

Software design

• You should use treat variables as immutable when there is no need to mutate the variables so use const instead of var to declare variables.
• variable names should describe the values they are holding to make code more readable. Your variable names don't tell anything making the code unnecessarily hard to read and if it was a more complex problem this could make your code unreadable.
• You should use template literals instead of concatenating strings, which will also make your code more readable.
• if you expect a number to be put in you can use type=number for the <input>. There are also more option like setting min and max which would make sense in your case as e.g. there is no negative money. See MDN docs.
• if you want to display something within the <input> use the placeholder attribute, not name.
• You can use valueAsNumber on an <input> element which will retrieve a number right away instead of a string. Together with input type number this will make sure you always get a number returned.

Working solution

function minitask() {
  const moneyAvailable = document.getElementById("money").valueAsNumber;
  if(moneyAvailable < 0) {
    alert(`You cannot buy anything with negative money!`)
    return;
  }
  const priceForIceCandy = 8.5;

  const noIceCandies = Math.floor(moneyAvailable / priceForIceCandy);
  const change = moneyAvailable - noIceCandies * priceForIceCandy; 
  alert(`You can buy ${noIceCandies} Icecandy and your change is ${change}`);
}

<input type="number" id="money" min="0" placeholder="Enter any amount">
<button onclick="minitask()">Calculate</button>

CodePudding user response：

• First you would need to check if the money is enough to buy something

• If it is you should divide the amount of money by the cost of an icecandy, it's true that the classic divider / doesn't give the change but there is an operator that does, which is called modulo

  then return all of that informations to the user

• Else if the user doesn't have enough money tell him that he needs more !