# Number Calculation : Number Data Type « Language Basics « JavaScript DHTML

Number Calculation

```

<html>
<title>Prices Demo</title>

<script language="javascript">

function calculation() {
var number= document.prices.quantity.value;
total = "" + Math.round((number*12.95)*100)/100;

if (total.indexOf(".") == -1)
total += ".00";
else if (total.indexOf(".") == total.length-2)
total += "0";

document.prices.subtotal.value = total += "\$";

}

</script>

<body>

<form name="prices">

<select name="quantity" onClick="calculation()">
<option value="0">0</option>

<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>

<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
</select>

<br>

<input type="text" name="subtotal" value="0.00\$">

</form>
</body>
</html>

```

### Related examples in the same category

 1 Define variables, assign values and output 2 Dividing by Zero 3 Add Four Numbers from an HTML Form (and Display the Results) 4 Add characters 5 Complex class to represent complex numbers 6 A Function That Returns the Sum of Three Numbers (Stripped-Down Version) 7 Concatenating Variables and Displaying the Value Contained 8 JavaScript Loan Calculator 9 Factorials 10 Converting a Number to a String 11 Creating Number Objects Rather than Performing String-to-Number Conversions 12 Using toString() with Radix Values 13 Using JavaScript Integers 14 Conversion of Logical Values to Numeric Values 15 Using Floating-Point Numbers 16 Automatic Conversion between Types 17 Explicit Conversion Functions 18 Date Object Calculations 19 Operator Precedence and Different Data Types 20 Converting Base 10 to Base 16 Using Bitwise Operators 21 Format a number 22 Format a number 2 23 Decimal to 2 Hex 24 Concatenate integer variable to a string variable