Monday, August 27, 2012

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:

OperatorDescriptionComparingReturnsTry it
==is equal tox==8falseTry it »
x==5trueTry it »
===is exactly equal to (value and type)x==="5"falseTry it »
x===5trueTry it »
!=is not equalx!=8trueTry it »
!==is not equal (neither value or type)x!=="5"trueTry it »
x!==5falseTry it »
>is greater thanx>8falseTry it »
<is less thanx<8trueTry it »
>=is greater than or equal tox>=8falseTry it »
<=is less than or equal tox<=8trueTry it »

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) x="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:

&&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.





If the variable age is a value below 18, the value of the variable voteable will be "Too young, otherwise the value of voteable will be "Old enough":
voteable=(age<18)?"Too young":"Old enough";

Try it yourself »

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