Mixin

es6mixin.js

var Bar1 = base => class extends base {
  componentWillMount(){
    super.componentWillMount();
    console.log('Bar1');
  }
};

var Bar2 = base => class extends base {
  componentWillMount(){
    super.componentWillMount();
    console.log('Bar2');
  }
};

class Foo extends mixins(Bar1, Bar2) {
  componentWillMount() {
    console.log('Foo before mixins');
    super.componentWillMount();
    console.log('Foo after mixins');
  }
}

mixins.js

function mixins(...mixinFactories) {
  var base = class {};
  // TODO: Add all possible method names that might call super()
  // to the base class so that they don't throw.
  for (var i = 0; i < mixinFactories.length; i++) {
     base = mixinFactories[i](base);
  }
  return base;
}

This is abusing the language capabilities. Mixin and inheritance are two different concepts with two different goals. For mixin, the support either should come from the language or you can just create instances of the mixin classes inside the host class and proxy to their methods.

@pmvald Could you elaborate on "create instances of the mixin classes inside the host class and proxy to their methods" please. I am trying to do that