gistfile1.js

var pureRender = (Component) => {
  Object.assign(Component.prototype, {
    shouldComponentUpdate (nextProps, nextState) {
      return !shallowEqual(this.props, nextProps) ||
             !shallowEqual(this.state, nextState);
    }
  });
};

module.exports = pureRender;

///////////////////////////////////////////////////
var pureRender = require('./pureRender');

class Foo extends React.Component {
  render () {
    return <div>this ain’t so bad</div>
  }
}

pureRender(Foo); // don't return so you know its mutative :(

module.exports = Foo;