JavaScript Comparison and Logical Operators
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:
| 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:
| if (age<18) document.write("Too young"); |
You will learn more about the use of conditional statements in the next chapter of this tutorial.
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:
| 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
| variablename=(condition)?value1:value2 |
Example
| 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".
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