是否可以从同一原型对象中的另一个属性创建一个属性？

Question

New to coding: I'm trying to do something like this in Javascript:

function Calculator(a,b){
 this.a=a;
 this.b=b;
 this.c=a*b;
 this.d=c;
}

var myTiCalc = new Calculator(1,2);
alert(myTiCalc.d);

So that it prints "d" in an alert box. However I keep getting a "Nan" in the alert.

Appreciate your expertise!

Answer 1

You will need to assign the var c .

Or you can do this.d = this.c;

 function Calculator(a,b){ this.a=a; this.b=b; this.eg = a*b; var c = a*b; this.d=c; this.d2 = this.eg; } var myTiCalc = new Calculator(1,2); console.log(myTiCalc.d); console.log(myTiCalc.d2); 

Answer 2

 function Calculator(a,b){ this.a=a; this.b=b; this.c=a*b; this.d=this.c; } var myTiCalc = new Calculator(1,2); alert(myTiCalc.d); 

In the line #5 you put this.d=c; instead of this.d=this.c . Variable c was not defined anywhere. What I think you need is to assign property c to d of the Calculator object, so you need to call it with the this keyword.