Hey Amazing people

Welcome to another blog in the JavaScript blog course.|

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In this blog, we aimed to study the Logical Operators of javascript.

Logical operators

There are four logical operators in JavaScript:

|| (OR)

&& (AND)

! (NOT)

?? (Nullish Coalescing)

Let's cover them in detail

|| (OR)

This is represented by 2 vertical lines.

result = a || b;

In classical programming, the logical OR is meant to manipulate boolean values only. If any of its arguments are true, it returns true, otherwise, it returns false.

There are 2 raised to power n operations possible. n = number of variables.

alert( 1 || 1 );   // true
alert( 0 || 1 );  // true
alert( 1 || 0 );  // true
alert( 0 || 0 ); // false

As we see, true this is the answer even if one is true(1).

You can understand OR as an add operator i.e. 1+0=1. etc.

OR only needs one value to be true and ultimately whole value becomes true.

Let's take an example

result = a || b || c

Now if any of one ( a or b or c ) is true, the whole result is true

and will not only depend on the other 2

&& (AND)

The AND operator is represented with two ampersands &&:

result = a && b;

In classical programming, AND returns true if both operands are truthy and false otherwise:

alert( true && true );   // true
alert( false && true );  // false
alert( true && false );  // false
alert( false && false ); // false

An example with if:

let hour = 12;
let minute = 30;

if (hour == 12 && minute == 30) {
  alert( 'The time is 12:30' );
}

Just as with OR, any value is allowed as an operand of AND:

if (1 && 0) { // evaluated as true && false
  alert( "won't work, because the result is falsy" );
}

On the contrary, it needs all values to be true to be true, and even if one value is false, the result would be false.

Let's take an example

result = a && b && c

Now if any of one ( a and b and c ) is false, the whole result is false

and needs all values to be true.

! (NOT)

The boolean NOT operator is denoted by the exclamation mark!

The syntax is straightforward:

answer = !value

if value is true we would get false and vice-versa.
The operator takes a single argument and performs the following actions:

The operand is converted to a boolean type: true/false. The inverse value is returned.

A resounding NO!! is occasionally used to convert a value to a boolean type:

alert( !!"non-empty string" ); // true
alert( !!null ); // false

That is, the first NOT changes the value to boolean and returns the opposite, followed by the second NOT. Finally, we have a simple value-to-boolean conversion.

A built-in Boolean function can achieve the same thing in a slightly more verbose manner:

alert( Boolean("non-empty string") ); // true
alert( Boolean(null) ); // false

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Logical operators in JavaScript