In JavaScript doing a simple shipping and handling calculation

Question

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 $

Answer 1

you can easily convert a string to a number

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

basically JS provides parseInt and parseFloat methods...

Answer 2

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 + ".");

Answer 3

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

Answer 4

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

Answer 5

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.

Answer 6

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

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