TypeScript Logical Operators

Logical AND operator – &&

If both operands (or expressions) are true, then result will be true, else false.

			let firstVar = true;
			let secondVar = false;

			console.log( firstVar && secondVar );	//false
			console.log( firstVar && true );		//true
			console.log( firstVar && 10 );			//10 which is also 'true'
			console.log( firstVar && '10' );		//'10'	which is also 'true'
			

Read More: Truthy and Falsy

Logical OR operator – ||

If any of the two operands (or expressions) are true, then result will be true, else false.

			let firstVar = true;
			let secondVar = false;

			console.log( firstVar || secondVar );	//true
			console.log( firstVar || true );		//true
			console.log( firstVar || 10 );			//true
			console.log( firstVar || '10' );		//true
			

Logical NOT operator – !

It is used to reverse the logical state of its operand. It converts true to false, and vice-versa.

			let firstVar = 10;
			let secondVar = 20;

			console.log( !true );		//false
			console.log( !false );		//true
			console.log( !firstVar );	//false
			console.log( !null );		//true