Data binding is a process of binding a UI component like textbox and code behind the object. For example, your input is:

<div className="post_input">
    
      <input className='post_data_input_overlay' placeholder="Ask your question here" ref="postTxt"/>

</div>

Data binding can be done using controlled input. Controlled input is gained by binding value to a state variable and onChange event to change the state as the input value changes.

class App extends React.Component {
  constructor() {
    super();
    this.state = {value : ''}
  }
  handleChange = (e) =>{ 
    this.setState({value: e.target.value});
  }
  render() {
    return (
    <div>
        <input type="text" value={this.state.value} onChange={this.handleChange}/>
        <div>{this.state.value}</div>
    </div>
   )
  }
}
ReactDOM.render(<App/>, document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.js"></script>
<div id="app"></div>