CyaSS React Component - mimic :hover and :active with inline styles

CyaSS.jsx

import React  from "react/addons";
import m      from "./m";

// https://www.youtube.com/watch?v=GOiVYbWJDOA
export default class CyaSS extends React.Component {
  constructor() {
    super();
    this.state = {
      hover: false,
      active: false
    };
  }

  _onHover(hover) {
    this.setState({
      hover: hover,
      active: this.state.active && hover
    });
  }

  _onActive(active) {
    this.setState({active: active});
  }

  _modifyStyle(style) {
    style = m(style,
      this.state.hover && style.hover,
      this.state.active && style.active);

    style.hover = undefined;
    style.active = undefined;

    return style;
  }

  _modifyChild(child) {
    return React.addons.cloneWithProps(child, {
      onMouseOver: this._onHover.bind(this, true),
      onMouseOut: this._onHover.bind(this, false),
      onMouseDown: this._onActive.bind(this, true),
      onMouseUp: this._onActive.bind(this, false),
      hover: this.state.hover,
      active: this.state.active,
      style: this._modifyStyle(child.props.style)
    });
  }

  render() {
    let child = React.Children.only(this.props.children);
    return this._modifyChild.call(this, child);
  }
}

example.jsx

import React from "react";
import CyaSS from "./CyaSS";

let linkStyle = {
  color: 'blue',
  hover: {color: 'green'},
  active: {color: 'red'}
};

React.render((
  <CyaSS>
    <a href="#" style={linkStyle}>Link</a>
  </CyaSS>
), document.body);

m.js

import objectAssign from "object-assign";

export default function m() {
  var res = {};
  for (let i in arguments) {
    if (arguments[i]) objectAssign(res, arguments[i]);
  }
  return res;
}