将对象属性设置为同一对象中属性的负值（Javascript / jQuery）

Question

Lets say I have a Javascript object:

var myObj = {
 property1 : 20,
 property2 : -20
}

But instead of -20 for property2 , I need to take the value of property1 and convert it to its negative within property2 :

var myObj = {
 property1 : 20,
 property2 : this.property1 * -1
}

This doesn't work, but I think it illustrates what I want to accomplish.

Answer 1

You can't do that. You can assign it later, though:

var myObj = {
    property1: 20
};

myObj.property2 = -myObj.property1;

Answer 2

I could suggest you the following

var myObj = {
    property1 : 20,
    get_property2 : function() {
        return this.property1 * -1;
    },
    set_property2 : function(value) {
        this.property1 = value * -1;
    }
}

Seems that this is a dependant property so it is readonly. But I've edited the code so that it is also writable.

Answer 3

You can use this:

var myObj = {
   property1 : 20,
   get property2() {    return this.property1 * -1;   }
};

But you can only read property2 property.

Defining setter of property2 will not be a problem. See JavaScript Getters and Setters link.