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JS Logical Operators

JavaScript

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In this tutorial we will learn about JavaScript logical operators.

We use the logical operator to compare two conditional statement to see if they satisfy the condition to execute a piece of code.

This is commonly used in conditional statements and loops.

We will learn about conditional statement and loop in their respective tutorial.

Following is a list of logical operators.

Operator	Symbol	Example
Logical AND	&&	x && y This will return true if value of both x and y is true.
Logical OR	\|\|	x \|\| y This will return true if value of either x or y is true.
Logical NOT	!	!x This will return true if value of x is false.

Note: x and y can be a variable or a conditional statements.

Click here for AND, OR and NOT logical gate tutorial.

Logical AND

In the following example we are checking whether variable x and y both are true.

var x = true;
var y = true;

console.log(x && y);	//this will print true

In the following example we are checking whether the two conditional statements are true.

var x = 10;
var y = -20;

console.log( (x > 0) && (y < 0) );	//this will print true

In the above code, (x > 0) is true because x is 10 and is greater than 0.

And (y < 0) is true because y is -20 and is less than 0.

Both the conditional statements are true so, the final result is also true.

Logical OR

In the following example we are checking whether variable x or y is true.

var x = true;
var y = false;

console.log(x || y);	//this will print true

In the above code, (x || y) is true because x is true. And to get true result we need only one side to be true.

var x = false;
var y = false;

console.log(x || y);	//this will print false

In the above code, (x || y) is false because both x and y are false.

Logical NOT

This operator works with one variable or conditional statement and inverts its value.

In the following example we are checking whether variable x is true.

var x = true;

console.log(!x);	//this will print false proving that x is true

In the above code, (!x) is false because x is true. And logical NOT inverts true to false.

var x = 10;
var y = 20;

console.log( !(x > y) );	//this will print true

In the above code, (x > y) is false because x is 10 and y is 20 so, x is less than y. And logical NOT of false value is true hence the result is true.

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