Ligning med én ubekendt i javascript

Kode 

function ligning(obj) {
    var count = 0;
    obj.a !== undefined && count++;
    obj.b !== undefined && count++;
    obj.c !== undefined && count++;
    if (count !== 2) {
        throw new "Exactly two of a, b and c must be set.";
    }
    if (obj.a === undefined) {
       obj.a = obj.b * obj.c;
    } else if (obj.b === undefined) {
       obj.b = obj.a / obj.c;
    } else {
       obj.c = obj.a / obj.b;
    }
    return obj;
}

alert(ligning({b:4, c:5}).a); //Alerter 4*5
alert(ligning({a: 20, b: 10}).c); //Alerter 20/10

JScript kode 

 //Funktionen laves
 function ligning(b, c) {
 a = b*c;
 return a;
 }
 
 ligning(2, 4); //Returnerer 8

JScript kode 

 //Funktionen laves
     function ligning(b, c) {
        return b*c;
     }
     ligning(2, 4); //Returnerer 8

Kode 

<script>
function ligning(){
  return {
    _a:null,
    _b:null,
    _c:null,
    a:function(v){if(arguments.length==1){this._a=v;return this;}else{return this._a}},
    b:function(v){if(arguments.length==1){this._b=v;return this;}else{return this._b}},
    c:function(v){if(arguments.length==1){this._c=v;return this;}else{return this._c}},
    calc:function(){
      if(this._a==null){
        this._a = this._b * this._c;
      }else if(this._b == null){
        this._b = this._a / this._c;
      }else if(this._c == null){
        this._c = this._a / this._b;
      }else{alert('error');}
      return this;
    }
  }
}

l = ligning().b(2).c(2.5).calc();
alert(l.a());
l = ligning().a(5).c(2.5).calc();
alert(l.b());
l = ligning().a(5).b(2).calc();
alert(l.c());
</script>