blah.js

class Blah {
  
  foo: null,
  someModel: null,
    
  constructor(args) {
    someModel = args.someModel;
    foo = new Foo({
      "fn": a
    });
    
    this.barBaz.handleSomething = this.a.bind(this, this.someModel)
  }

  a: function(someModel, event) {
    return function (event) {
      someModel.baz(event);
    }
  }
}

class Foo {
  
  constructor: function(args) {
    this.someModel = args.someModel;
    this.handleStuff = args.fn.bind(this, this.someModel)
  }
}

// I want to pass a down the component tree twice to Foo's child so I can execute a. Foo's child will also have a someModel to execute on.