React auto-completion component

AutoCompletionInput.js

var AutoCompletionInput = React.createClass({
  getInitialState: function() {
    return {completion:'',prevText:''};
  },
  getCompletion : function(txt){
    if (txt.length === 0|| this.state.prevText.length>=txt.length) return '';
    var finder = function(x){return x.startsWith(txt)}.bind(this);
    var repl = this.props.completionValues.find(finder);
    if (!repl) return '';
    else return repl.substring(txt.length);
  },
  componentDidUpdate: function () {
    var input = this.getDOMNode(),
    text = this.props.value,
    comp = this.state.completion;
    input.focus();
    input.setSelectionRange(text.length-comp.length, text.length);
  },
  onChange: function(e) {
    var txt = e.target.value;
    var comp = this.getCompletion(txt);
    this.setState({completion:comp,prevText:txt});
    this.props.onChange(txt+comp);
  },
  render: function(){
    var value = this.props.value;
    return <input onChange={this.onChange} value={value} />;
  }
});