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

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

class Foo extends mixins(Bar1, Bar2) {
  componentWillMount() {
    super.componentWillMount();
  }
}