JAVASCRIPT

ref.current.selectionStart

handleKeyDown(event) {
    if (event.keyCode === 9) { // tab was pressed
        event.preventDefault();
        var val = this.state.scriptString,
            start = event.target.selectionStart,
            end = event.target.selectionEnd;

        this.setState({"scriptString": val.substring(0, start) + '	' + val.substring(end)});
        // This line doesn't work. The caret position is always at the end of the line
        this.refs.input.selectionStart = this.refs.input.selectionEnd = start + 1;
    }
}
onScriptChange(event) {
   this.setState({scriptString: event.target.value});
}
render() {
    return (
        <textarea rows="30" cols="100" 
                  ref="input"
                  onKeyDown={this.handleKeyDown.bind(this)}
                  onChange={this.onScriptChange.bind(this)} 
                  value={this.state.scriptString}/>
    )
}

ref.current.selectionStart

handleKeyDown(event) {
      if (event.keyCode === 9) { // tab was pressed
          event.preventDefault();
          var val = this.state.scriptString,
          start = event.target.selectionStart,
          end = event.target.selectionEnd;
          this.setState(
              {
                  "scriptString": val.substring(0, start) + '	' + val.substring(end)
              },
              () => {
                  this.refs.input.selectionStart = this.refs.input.selectionEnd = start + 1
              });
      }
 }