React.findDOMNode comes as undefined

Question

I have

<div id="wrapper"></div>

<script type="text/jsx">
/* @jsx React.DOM*/
var Login = React.createClass({
    Validate: function(){
        debugger;
        var username = React.findDOMNode(this.refs.username).trim();
        var password = React.findDOMNode(this.refs.password).trim();
        console.log('Username: ' + username + '\nPassword: ' + password);
        if(username == 'username' && password == 'password'){
            alert('Success');
        }
        else{
           alert('Failure');
        }
    },
    Clear: function(){

    },
    render: function(){
        return(
            <div className="container">
                Login 
                <p></p>
                Username: <input type="text" ref="username" /><br />
                Password: <input type="password" ref="password" /><br /><br />
                <input type="button" value="Submit" onClick={this.Validate} />&nbsp;&nbsp;
                <input type="button" value="Clear" onClick={this.Clear} />
            </div>
        );
    }
});

React.render(<Login />, document.getElementById('wrapper'))
</script>

Answer 1

React.findDOMNode was introduced in React v0.13, so make sure you are using at least v0.13.