This is an example of how to build a counter with React.

ReactExample

/** @jsx React.DOM */

var LikeButton = React.createClass({
  getInitialState: function() {
    return {liked: false};
  },
  handleClick: function(event) {
    this.setState({liked: !this.state.liked});
  },
  render: function() {
    var text = this.state.liked ? 'like' : 'unlike';
    return (
      <p onClick={this.handleClick}>
        You {text} this. Click to toggle.
      </p> a
    );
  }
});


var CashCounter = React.createClass({
    getInitialState: function() {
        return {cashAmount: 0};
    },
    handleSubmit: function(){
        var text = document.getElementById("thebox").value;
        var numba = parseFloat(text)
        if(!numba) return;
        
        var num = numba + parseFloat(this.state.cashAmount);
        var theVal = num.toString();
        this.setState({cashAmount: theVal});
    },
    render: function() {
    return (
        <div>
        <p > You have gathered {this.state.cashAmount} dollars. That's way more than Amer!</p>
        <input type="textbox" id="thebox" />
        <input type="button" id="submit" value="submit" onClick={this.handleSubmit}/>
        </div>
        );
    }
});

React.renderComponent(
  <CashCounter />,
  document.getElementById('hi')
);