React mixin thing

mixins.js

function mixin(){
  var privatevar = 5;
  
  this.on('componentWillMount', () =>{
    //stuff
  })
  
  this.mixinMethod = () => {
    return privatevar;
  }
}

class App extends React.Component {
  
  constructor(props, context){
    super()
    
    mixin.call(this)
  }
  
  render(){
    
  }
}