Conditionals

Steuerlogik für Entscheidungen Codepfade werden abhängig von Bedingungen ausgeführt.

if Statement

---

const isMailSent = true;  
if (isMailSent) {   
	console.log('Mail sent to recipient'); 
}

Ternary Operator

---

var x=1;  
result = (x === 1) ? true : false;

Operators

---

OR

true || false;       // true 
10 > 5 || 10 > 20;   // true 
false || false;      // false 
10 > 100 || 10 > 20; // false

AND

true && true;        // true 
1 > 2 && 2 > 1;      // false 
true && false;       // false 
4 === 4 && 3 > 1;    // true

Comparison Operators

1 > 3                // false 
3 > 1                // true 
250 >= 250           // true 
1 < 3                // true
3 < 1                // false 
250 <= 250           // true
1 === 1              // true 
1 === 2              // false 
1 !== 1              // false
1 !== 2              // true 

vs =

The == just check the value, === check both the value and the type.

 
0 == false   // true 
0 === false  // false, different type 
1 == "1"     // true,  automatic type conversion  
1 === "1"    // false, different type 
null == undefined  // true 
null === undefined // false 
'0' == false       // true 
'0' === false      // false

Logical Operator !

let lateToWork = true; 
let oppositeValue = !lateToWork;  // => false

Nullish coalescing operator ??

null ?? 'I win';           //  'I win' 
undefined ?? 'Me too';     //  'Me too'  
false ?? 'I lose'          //  false 
0 ?? 'I lose again'        //  0 
'' ?? 'Damn it'            //  ''

else if

---

const size = 10;  
if (size > 100) {   
	console.log('Big'); 
} else if (size > 20) {   
	console.log('Medium'); 
} else if (size > 4) {   
	console.log('Small'); 
} else {   
	console.log('Tiny'); 
}

switch Statement

---

const food = 'salad';  
switch (food) {   
	case 'oyster':     
		console.log('The taste of the sea');     
		break;   
	case 'pizza':     
		console.log('A delicious pie');     
		break;   
	default:     
		console.log('Enjoy your meal'); }