无法访问在 ZDE9B9ED78D7E2E1DCEEFFEE780E2F91 中另一个 object 的 function 内部创建的 object 的属性

Question

 function Method1(a, b, c) { this.a = a; this.b = b; this.c = c; } Method1.prototype = { add: function() { let x = this.a * Method2.r + this.b + this.c; console.log(x); } } function Method2(a, b, c, r) { this.r = r; this.obj = new Method1(a, b, c); } Method2.prototype = { print: function() { this.obj.add(); } } let x = new Method2(1, 2, 3, 4); x.print();

In the above sample code, I want to use the variable r of Method2 inside of Method1's add function. Can anyone please tell me where I am doing wrong and how to solve this? I need to access r inside add()

Answer 1

A workaround for you is to declare this.r for Method1 . This way Method1 has can accept the r from Method2 and use it in the add function. See the attached snippet.

 function Method1(a, b, c, r) { this.a = a; this.b = b; this.c = c; this.r = r; } Method1.prototype = { add: function() { let x = this.a * this.r + this.b + this.c; console.log(x); } } function Method2(a, b, c, r) { this.r = r; this.obj = new Method1(a, b, c, r); } Method2.prototype = { print: function() { this.obj.add(); } } let x = new Method2(1, 2, 3, 4); x.print();

Answer 2

Consider making r in Method2 a static variable so that you can use it globally like this:

function Method1(a, b, c) {
    this.a = a;
    this.b = b;
    this.c = c;
}
Method1.prototype = {
    add: function() {
        let x = this.a * Method2.r + this.b + this.c;
        console.log(x);
    }
}

function Method2(a, b, c, r) {
    Method2.r = r; // This is the only change you need to make
    this.obj = new Method1(a, b, c);
}

Method2.prototype = {
    print: function() {
        this.obj.add();
    }
}

let x = new Method2(1, 2, 3, 4);
x.print();

Answer 3

Did a little changes to your code:

function Method1(a, b, c) {
  this.a = a;
  this.b = b;
  this.c = c;
};
Method1.prototype.add = function(r){
  let x = this.a * r + this.b + this.c;
  console.log(x);
};
function Method2(a, b, c, r) {
  this.r = r;
  this.obj = new Method1(a, b, c);
}

Method2.prototype.print= function() {
  this.obj.add(this.r);
};

The problems were

1. You were defining prototype functions wrong so instead of

   Method2.prototype = { print: function() { this.obj.add(); }}

   you should use:

   Method2.prototype.print = function() {this.obj.add();}

2. Method2 is independent of Method1, so in order to use the "r" from Method2 in Method1 it needs to be passed from Method2 to Method1.