CODEWITHSUNDEEP
javascript
Nicole
Nicole

Reputation: 15

In JavaScript doing a simple shipping and handling calculation

I am having trouble with a simple JavaScript calculation. My document is supposed to add $1.50 to an order if it is $25 or less, or add 10% of the order if it is more then $25. The exact problem is:

Many companies normally charge a shipping and handling charge for purchases. Create a Web page that allows a user to enter a purchase price into a text box and includes a JavaScript function that calculates shipping and handling. Add functionality to the script that adds a minimum shipping and handling charge of $1.50 for any purchase that is less than or equal to $25.00. For any orders over $25.00, add 10% to the total purchase price for shipping and handling, but do not include the $1.50 minimum shipping and handling charge. The formula for calculating a percentage is price * percent / 100. For example, the formula for calculating 10% of a $50.00 purchase price is 50 * 10 / 100, which results in a shipping and handling charge of $5.00. After you determine the total cost of the order (purchase plus shipping and handling), display it in an alert dialog box.

This is my code:

    var price = window.prompt("What is the purchase price?", 0);
var shipping = calculateShipping(price);
var total = price + shipping;
function calculateShipping(price){
if (price <= 25){
 return 1.5;
}
else{
 return price * 10 / 100
}
}
window.alert("Your total is $" + total + ".");

When testing I enter a number in the prompt box, and instead of calculating as if I entered a number it calculates as if I entered a string. i.e. i enter 19 and it gives me 191.5 or I enter 26 and it gives me 262.6

Upvotes: 1

Views: 6927

Answers (6)

k rey
k rey

Reputation: 631

var price = parseFloat(window.prompt("What is the purchase price?", 0)); 
var shipping = calculateShipping(price); 
var total = price + shipping; 
function calculateShipping(price){ 
  var num = new Number(price);
  if (num <= 25){  
    return 1.5; 
  } else{  
    return num * 10 / 100 
  } 
} 
window.alert("Your total is $" + total + ".");

This should do it for you.

Upvotes: 0

Blender
Blender

Reputation: 298196

A bit of redundant multiplication, but your problem is that the numbers that are being inputted are treated as strings, not numbers. You have to convert them to floating point numbers:

var price = parseFloat(window.prompt("What is the purchase price?", 0));
var shipping = calculateShipping(price);
var total = price + shipping;

function calculateShipping(price)
{
  if (price <= 25)
  {
   return 1.5;
  } else {
    return price / 10
  }
}

window.alert("Your total is $" + total + ".");

Upvotes: 0

Phrogz
Phrogz

Reputation: 303254

See my answer to the s/o question "Javascript adding two numbers incorrectly".

Upvotes: 0

Dutchie432
Dutchie432

Reputation: 29160

Actually, you need to cast your text results into float values using parseFloat()

http://www.w3schools.com/jsref/jsref_parseFloat.asp

Upvotes: 0

Mutation Person
Mutation Person

Reputation: 30498

Using parseFloat will help you:

var price = parseFloat(window.prompt("What is the purchase price?", 0))
var shipping = parseFloat(calculateShipping(price));
var total = price +shipping;
function calculateShipping(price){
if (price <= 25){
 return 1.5;
}
else{
 return price * 10 / 100
}
}
window.alert("Your total is $" + total + ".");

See it working at: http://jsfiddle.net/e8U6W/

Also, a little-known put more performant way of doing this would be simply to -0:

var price =window.prompt("What is the purchase price?", 0) - 0;

(See: Is Subtracting Zero some sort of JavaScript performance trick?)

Be sure to comment this, though as its not as obvious to those reading your code as parseFloat

Upvotes: 2

hvgotcodes
hvgotcodes

Reputation: 120198

you can easily convert a string to a number

http://www.javascripter.net/faq/convert2.htm

basically JS provides parseInt and parseFloat methods...

Upvotes: 0

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