Comparison and Logical operators are used to test for true or false.

Comparison Operators

Comparison operators are used in logical statements to determine equality or difference between variables or values.

Given that x=5, the table below explains the comparison operators:
Code:
Operator        Description                                    Example
==                is equal to                                    x==8 is false 
===                is exactly equal to (value and type)        x===5 is true   x==="5" is false 
!=                 is not equal                                 x!=8 is true 
>                 is greater than                             x>8 is false 
<                 is less than                                 x<8 is true 
>=                 is greater than or equal to                 x>=8 is false 
<=                 is less than or equal to                     x<=8 is true
How Can it be Used

Comparison operators can be used in conditional statements to compare values and take action depending on the result:
Code:
if (age<18) document.write("Too young");
Logical Operators



Logical operators are used to determine the logic between variables or values.

Given that x=6 and y=3, the table below explains the logical operators:
Code:
Operator    Description        Example 
&&             and             (x < 10 && y > 1) is true 
||             or                 (x==5 || y==5) is false 
!             not             !(x==y) is true
Conditional Operator

JavaScript also contains a conditional operator that assigns a value to a variable based on some condition.


Syntax
Code:
variablename=(condition)?value1:value2


Example

Code:
greeting=(visitor=="PRES")?"Dear President ":"Dear ";
If the variable visitor has the value of "PRES", then the variable greeting will be assigned the value "Dear President " else it will be assigned "Dear".