TextareaAutoSize -- yet another

TextareaAutoSize.js

import React, {PropTypes} from 'react'

export default class TextareaAutoSize extends React.Component {
  constructor(props) {
    super(props);
  }

  recalcHeight() {
    var borders = 2;
    var innerHeight = Math.floor(this.textarea.scrollHeight / 2) * 2 + 1;
    this.textarea.style.height = (innerHeight + borders) + 'px';
  }

  componentDidMount() {
    this.recalcHeight();
  }

  handleChange(e) {
    this.textarea.style.height = 0;
    this.recalcHeight();
    if (this.props.onChange) this.props.onChange(e.target.value)
  }

  focus() {
    if (this.textarea)
      this.textarea.focus();
  }

  render() {
    return <textarea
      {...this.props}
      ref={t => this.textarea = t}
      rows="1"
      onChange={e => this.handleChange(e)}
    />
  }
}