如何在构造函数中创建一个JS对象，并将“父对象”作为构造函数参数？

Question

The question might sound a bit confusing so I'll let the code explain:

 function Foo(arg) { const argument = arg; const fooPart = new FooPart(this); this.printArg = function() { console.log(argument); } } function FooPart(foo) { this.parent = foo; this.parent.printArg(); } let foo = new Foo("this is the argument"); 

This is not working for me. How can I solve this problem or better - what would be the correct approach for this?

Thanks

Answer 1

 function Foo(arg) { this.argument = arg; this.fooPart = new FooPart(this); } Foo.prototype.printArg = function() { console.log(this.argument); } function FooPart(foo) { this.parent = foo; this.parent.printArg(); } let foo = new Foo("this is the argument"); 

1. You should call FooPart after printArg definition
2. You should use this.parent to access parent

Answer 2

The problem is that you define printArg after trying to call it.

The traditional way to define a "class" which doesn't have this problem would be:

 function Foo(arg) { this.argument = arg; this.fooPart = new FooPart(this); } Foo.prototype.printArg = function() { console.log(this.argument); } function FooPart(foo) { this.parent = foo; this.parent.printArg(); } let foo = new Foo("this is the argument"); 

The more modern version to define an "actual" class is:

 class Foo { constructor(arg) { this.argument = arg; this.fooPart = new FooPart(this); } printArg() { console.log(this.argument); } } class FooPart { constructor(foo) { this.parent = foo; this.parent.printArg(); } } let foo = new Foo("this is the argument");