!!! Listings aus dem Artikel "Klassentreffen" von Stefan Mintert in
!!! iX 8/2015, S. 123

!!! Listing 1

@ü.li:Listing 1: Neues Schlüsselwort let

function declaredWithVar() {
  var x = 1;
  if (x > 0) {
    var x = 2;  // gleiche Variable!
    console.log(x);  // 2
  }
  console.log(x);  // 2
}

function declaredWithLet() {
  var x = 1;
  if (x > 0) {
    let x = 2;  // eigener Scope
    console.log(x);  // 2
  }
  console.log(x);  // 1
}

function declaredWithLateVar() {
  console.log(x);  // undefined
  if (true) {
    var x = 2;  // eigener Scope
    console.log(x);  // 2
  }
  var x = 1;
  console.log(x);  // 1
}

function undeclared() {
  console.log(x);  // Fehler und Programmabbruch
  if (true) {
    console.log(x);  // 2
  }
  console.log(x);  // 1
}

console.log('// declaredWithVar');
declaredWithVar();

console.log('// declaredWithLet');
declaredWithLet();

console.log('// declaredWithLateVar');
declaredWithLateVar();

console.log('// undeclared');
undeclared();

 

!!! Listing 2

@ü.li:Listing 2: Vererbung mit Prototyping

function Vehicle() {
	 var gear = 0;

	 this.upshift = function() {
	   gear++;
	   return gear;
	 }

	 this.downshift = function() {
	   gear = Math.max(gear--, 0);
	   return gear;
	 }
   
   this.getGear = function() {
       return gear;
   }
}

function Bicycle() {
	 this.numberOfWheels = 2;
}

Bicycle.prototype = new Vehicle();

function Car() {
	 this.numberOfWheels = 4;
}

Car.prototype = new Vehicle();


var a = new Bicycle();

console.log(a.upshift()); // 1
console.log(a.getGear());        // 1
console.log(a.numberOfWheels);     // 2

var b = new Car();

console.log(b.upshift()); // 1
console.log(b.getGear());        // 1 
console.log(b.numberOfWheels);     // 4


!!! Listing 3

@ü.li:Listing 3: Vererbung mit Klassen

class Vehicle {
    constructor() {
	this.currentGear = 0;	
    }

    upshift() {
	this.currentGear++;
	return this.currentGear;
    }
    
    downshift() {
	currentGear = Math.max(this.currentGear--, 0);
	return this.currentGear;
    }
    
    set gear(g) {
	this.currentGear = g;
    }
    
    get gear() {
	return this.currentGear;
    }    
}

class Car extends Vehicle {
    constructor() {
	super();
	this.numberOfWheels = 4;
    }
}

class Bicycle extends Vehicle {
    constructor() {
	super();
	this.numberOfWheels = 2;
    }
}

var a = new Bicycle();

console.log(a.upshift()); // 1
console.log(a.gear);             // 1
console.log(a.numberOfWheels);     // 2

var b = new Car();

console.log(b.upshift()); // 1
console.log(b.gear);             // 1
console.log(b.currentGear);      // 1
console.log(b.numberOfWheels);     // 4


!!! Listing 4

@ü.li:Listing 4: Potenzfunktion mit Array aufrufen

function pow(b, e=2) {
    return Math.pow(b, e);
}
function powArray(basis, ...expArray) {
    return expArray.map(function(exp) {
            return pow(basis,exp);
    });
}
console.log(powArray(2,0,1,2,3,4,5,6,7,8,9,10)); 
// [ 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 ]

!!! Listing 5

@ü.li:Listing 5: Zwei Adressen

let addressA = {
    name: "Max Mustermann",
    street: "Haupstrasse 5",
    zip: "01234",
    city: "Berlin"
};
let addressB = {
    name: "Moritz Mustermann",
    street: "Praterstraße 1",
    zip: "1180",
    city: "Wien",
    country: "Österreich"
};

// Konsolenausgabe
console.log(proxiedAddressA.country); // Deutschland
console.log(proxiedAddressB.country); // Österreich

!!! bitte Linie ziehen
// zwei let-Statements
let proxiedAddressA = new Proxy(addressA, addressHandler);
let proxiedAddressB = new Proxy(addressB, addressHandler);

!!! Listing 6

@ü.li:Listing 6: Proxy-Handler

let addressHandler = {
    get(originalObject, property) {
	console.log("GET " + property);
	if (originalObject[property]) {		// (1)
	    return originalObject[property];
	} else if (property == "country") {     // (2)
	    return "Deutschland";
	} else {
            return;				// (3)
	}
    }
};

!!! Listing 7

@ü.li:Listing 7: Promise: Versprechen geben

function fragSpaeter(verzug = 1000, frage) {
  return new Promise(function(fulfill, reject) {
      console.log("// 1");
      setTimeout(function() {
         console.log("// 2");
         let antwort = confirm(frage);
	 if (antwort) {
		fulfill("Du hast Ja gesagt");
	 } else {
		fulfill("Du hast Nein gesagt");
	 }
      }, verzug)
  });
}

!!! Listing 8

@ü.li:Listing 8: fragSpaeter: neues Versprechen

fragSpaeter(5000,'Ja oder Nein?').then(function(result) {
    console.log("Fulfilled: " + result); // "Fulfilled: Du hast Ja gesagt"
}, function(err) {
    console.log("Rejected: " + err); // "Rejected: Du hast Nein gesagt"
});
console.log("// 3");

!!! Listing 9

@ü.li:Listing 9: Endrekursion

function summeA(x, sum=0) {
    let newX = 0;

    if (x < 1) {
	return sum;
    } 

    newX = summeA(x - 1, sum + x);
    return newX;
}