# Using Javascript number operators

## Mathematical Number operators.

• To create numeric expressions we are using mathematical operators which can be:
+
``````var sum1=50, sum2=30;
var sum = sum1 + sum2;
// sum will be 80 ``````
Used to add one operand with another operand.
-
(subtraction)
``````var sum1=50, sum2=30;
var sum = sum1 - sum2;
// sum will be 20 ``````
Used to subtract one operand with another operand.
*
(multiplication)
``````var price=10, quantity=5;
var sum = price * quantity;
// sum will be 50 ``````
Used to multiplicate one operand with another operand.
/
(division)
``````var price=10, sum=5;
var quantity = sum / price;
// quantity will be 0.5 ``````
Used to devide one operand with another operand.
%
(modulo)
``````var price=5, sum=11;
var rest = sum % price;
// rest will be 1``````
Used to get remainder from one operand with another operand.
-
(unary)
``````var sum2=11;
var sum = -sum2;
// sum will be -11``````
Converts a positive value to an equivalently negative value, and vice versa.
+
(unary)
``````var sum2=11;
var sum = +sum2;
// sum will be 11``````
The operator does nothing; it simply evaluates to the value of its argument.
• Expression can also be of incrementing and decrementing types:
`````` var count=10
// OR
count = count + 1;    // Start with count and increment it with a value (1).
counter = count - 1;  // Start with count and decrement it with a value (1).
// OR
count += 1;           // Start with count and increment it with a value (1).
count -= 1;           // Start with count and decrement it with a value (1).``````
The two first one has both two options which is prefix and postfix:
``````var a = ++c;      // prefix operator - increments c and assign it to a
var b = c++;      // postfix operator - assign c to b and then increment c
var a = --c;      // prefix operator - decrements c and assign it to a
var b = c--;      // postfix operator - assign c to b and then decrement c``````
Program example using prefix and postfix with incrementing and decrementing:
``````<script type="text/javascript">
var value = 1;
var result = value++ * 5;
document.write("result: "+ result);
document.write(" and value: "+  value);
document.write("<br>");
// prints: result: 5 and value: 2
document.write("result: "+ --result);
document.write(" and value: "+  value++);
document.write("<br>");
// prints: result: 4 and value: 2
// but the result=4 and the value=3
result = (++value * 5) ;
document.write("result: "+ result);
document.write(" and value: "+  value);
document.write("<br>");
// prints: result: 20 and value: 4
document.write("result: "+ ++result);
document.write(" and value: "+  --value);
document.write("<br>");
// prints: result: 21 and value: 3
</script>``````