component.jsx

var DocumentEdit = React.createClass({
  mixins: [CoerceDocumentMixin, PerfMixin],
  ....
});

mixin.js

module.exports = {
  getInitialState() {
    return {
      document: this._coerceDocument(this.props.document)
    }
  },

  _updateDocument(doc) {
    this.setState({
      document: _coerceDocument(doc)
    });
  },
  
  _coerceDocument(data) {
    var doc = Object.assign({ }, this.state.document, data);
    
    //... do stuff to 'doc'
    return doc;
  }
};