Passing react text field input values as parameters to a method

Question

I have the below input fields of which I need to get the entered inputs and pass it to the onClick event of the button shown below.

Answer 1

How can I achieve this without storing the values in states?

I think in this case better use states

class App extends React.Component {
  constructor() {
    super();
    this.state = {
      topicBox: null,
      payloadBox: null
    };
    
    this.publish = this.publish.bind(this);
    this.handleChange = this.handleChange.bind(this);
  }
  
  handleChange({ target }) {
    this.setState({
      [target.name]: target.value
    });
  }

  publish() {
    console.log( this.state.topicBox, this.state.payloadBox );
  }
  
  render() {
    return <div>
      <input 
        type="text" 
        name="topicBox" 
        placeholder="Enter topic here..." 
        value={ this.state.topicBox }
        onChange={ this.handleChange } 
      />
      
      <input 
        type="text" 
        name="payloadBox" 
        placeholder="Enter payload here..."
        value={ this.state.payloadBox } 
        onChange={ this.handleChange } 
      />
      
      <button value="Send" onClick={ this.publish }>Publish</button>
    </div>
  }
}

ReactDOM.render(<App />, document.getElementById('container'));

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

Answer 2

You can add ref for each text field, and read the value from it like:

class App extends React.Component {
  constructor() {
    super();
    this.publish = this.publish.bind(this);
  }

  publish(topicBox, payloadBox) {
    alert(this.refs.topic.value);
    alert(this.refs.payload.value);
  }

  render() {
    return <div>
      <input 
        ref="topic"
        type="text"
        name="topicBox"
        placeholder="Enter topic here..."/>

      <input 
        ref="payload"
        type="text"
        name="payloadBox"
        placeholder="Enter payload here..."/>

      <button 
        value="Send"
        onClick={this.publish}> 
        Publish
      </button>
    </div>
  }
}

ReactDOM.render(<App />, document.getElementById('container'));

Working fiddle https://jsfiddle.net/hjx3ug8a/15/

Thanks for Alexander T for his addition!