如何将对象中的属性分配给javascript中同一对象中某个属性的值？

Question

In code below I'm creating a circle objects and giving it's keys some values. I'm setting the radius property of the circle object to it's diameter divided by 2. When we console.log it's value, it returns NAN. How to fix this problem?

let circle = {
    posX: 40,
    posY: 70,
    diameter: 30,
    radius: this.diameter/2
}
console.log(circle.radius)

Answer 1

You need a method inside the object in order to do it, because you are using the this keyword, and it needs a function to work:

 let circle = { posX: 40, posY: 70, diameter: 30, radius: function () { return this.diameter/2; } } console.log(circle.radius())

Answer 2

You can use a class:

class Circle {
   posX;
   posY;
   diameter;
   radius;
   
   constructor(posX, posY, diameter){
    this.posX = posX;
    this.posY = posY;
    this.diameter = diameter;
    this.radius = diameter / 2;
   }
}

Then when you instanciate it like the following, the radius is automatically set to diameter/2

let circle = new Circle(40, 70, 30);
// circle.radius is 15