Why is my console is say NaN is class extend Javascript-CodePudding

So I was making project and when I try to get the parameter from class parent its say NaN while the other is true. Here the code:

class transportasi {//class parent
  constructor(nama,roda,pintu){
  this.nama = nama
  this.roda = roda
  this.pintu = pintu

  }
}

class mobil extends transportasi{//Class Children
  constructor(roda,lampu){
    super(roda)//the problem
    this.lampu = lampu
  }

  jmlahfeature(){
    return this.lampu   this.roda 
  }
}
const mobil1 = new mobil(2,4)//the problem

//I cant fill the value of roda only lampu
console.log("Hasil Perhitungan Feature mobil : "   mobil1.jmlahfeature())

I want it so I can fill the value of parameter roda. So it doesn't say NaN in console.

CodePudding user response：

As Ivar points out correctly roda is the second parameter and you pass only the first parameter in the super().

The following code should give your desired result.

class transportasi {//class parent
    constructor(nama,roda,pintu){
    this.nama = nama
    this.roda = roda
    this.pintu = pintu
    
    }
}

class mobil extends transportasi{//Class Children
    constructor(roda,lampu){
        super('here should be some value', roda) 
        this.lampu = lampu
    }
    
    jmlahfeature(){
        return this.lampu   this.roda 
    }
}
const mobil1 = new mobil(2,4)//the problem

//I cant fill the value of roda only lampu
console.log("Hasil Perhitungan Feature mobil : "   mobil1.jmlahfeature())

CodePudding user response：

You did not assign any value to this.roda = roda You can try this out.

class transportasi {//class parent
    constructor(nama,roda,pintu){
    this.nama = nama
    this.roda = roda
    this.pintu = pintu
  
    }
  }
  
  class mobil extends transportasi{//Class Children
    constructor(roda,lampu){
      super(roda)//the problem
      this.roda = roda
      this.lampu = lampu
    }
  
    jmlahfeature(){
      return this.lampu   this.roda 
    }
  }
  const mobil1 = new mobil(2,4)//the problem
  
  //I cant fill the value of roda only lampu
  console.log("Hasil Perhitungan Feature mobil : "   mobil1.jmlahfeature())

CodePudding user response：

Rather than individual arguments for the parent and child classes you supply a single object with named properties. A simple test within the child class can assign a default value if the required property has not been assigned to the parent arguments.

class transportasi {
  constructor(args = {}) {
    args = Object.assign({
      nama: false,
      roda: false,
      pintu: false
    }, args);

    this.nama = args.nama;
    this.roda = args.roda;
    this.pintu = args.pintu;
  }
}

class mobil extends transportasi {
  constructor(args = {}) {
    super(args)
    this.lampu = args.lampu || 0;
  }
  jmlahfeature() {
    return this.lampu   this.roda
  }
}


/* correctly named property - Maths should succeed */
const args = {
  lampu: 2,
  roda: 4
};
const app1 = new mobil(args);
console.log(app1.jmlahfeature());

/* incorrectly named, default value of zero used */
const bogus = {
  xlamxpu: 23,
  roda: 33
}
const app2 = new mobil(bogus);
console.log(app2.jmlahfeature());