JavaScript Course | Logical Operators in JavaScript

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There are three logical operators in Javascript:

!(NOT)
&&(AND)
||(OR)

!(NOT)
It reverses the boolean result of the operand (or condition).

result = !value;

The following operator accepts only one argument and does the following:

Converts the operand to boolean type i.e true/false
returns the flipped value

Example:

<script> 
// !(NOT) operator 
let geek = 1; 
alert(!geek); 
</script> 

Output:

false

The operator converted the value ‘1’ to boolean and it resulted in ‘true’ then after it flipped(inversed) that value and that’s why when we finally alert the value we get ‘false’.

&&(AND)
The && operator accepts mutilple arguments and it mainly does the following:

Evaluates the operands from left to right
For each operand, it will first convert it to a boolean. If the result is false, stops and returns the original value of that operand.
otherwise if all were truthy it will return the last truthy value.

result = a && b; // can have mutiple arguments.

Example:

<script> 
// &&(AND) operator 
alert( 0 && 1 ); // 0 
alert( 1 && 3 ); // 3 
alert( null && true ); // null 
alert( 1 && 2 && 3 && 4); // 4 
</script> 

Output:

0
3
null 
4

||(OR)
The ‘OR’ operator is somewhat opposite of ‘AND’ operator. It does the following:

evaluates the operand from left to right.
For each operand, it will first convert it to a boolean. If the result is true, stops and returns the original value of that operand.
otherwise if all the values are falsy, it will return the last value.

result = a || b;

Example:

<script> 
// ||(OR) Operator 
alert( 0 || 1 ); // 1 
alert( 1 || 3 ); // 1 
alert( null || true ); // true 
alert( -1 || -2 || -3 || -4); // -1 
</script> 

Output:

1
1
true
-1

Next article: JavaScript Course | Conditional Operator in JavaScript

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