My Reactjs Code Says Uncaught TypeError: Cannot read property 'value' of null
<p>I Am Trying To Make A Programme Which Displays The Changes Made In Input Value To Output Box But Getting Error Like Uncaught Type Error: Cannot read property 'value' of null And I Have No Idea What Is The Error Here</p>

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<pre class="snippet-code-js lang-js prettyprint-override"><code>var App =React.createClass({
    getInitialState:function(){
        return{
            value:"My Value"
        }
    },
    updateValue:function(modifiedValue){
        this.setState({
            value:modifiedValue
        })
    },
    render:function(){
        return(
            &lt;div className="inputBox container-fluid"&gt;
                &lt;h1 className="text-center text-primary"&gt;Hello FreeCodeCampers !!!&lt;/h1&gt;
                &lt;div className="row col-md-12"&gt;
                    &lt;InputBox value={this.state.value} updateValue={this.updateValue}/&gt;
                    &lt;h1&gt;{this.state.value}&lt;/h1&gt;
                &lt;/div&gt;
            &lt;/div&gt;
        );
    }
});
var InputBox =React.createClass({
    update:function(){
        var modifiedValue=ReactDOM.findDOMNode(this.refs.inputValue).value;
        this.props.updateValue(modifiedValue);
    },
    render:function(){
        return(
            &lt;input type="text" value={this.props.value} onChange={this.update} ref="initialValue"/&gt;
        );
    }
});
ReactDOM.render(&lt;App /&gt;,
document.querySelector("#app")
);</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;!DOCTYPE html&gt;
&lt;head&gt;
    &lt;meta charset="UTF-8" /&gt;
    &lt;title&gt;React Tutorial&lt;/title&gt;
    &lt;link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css"&gt;
    &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"&gt;&lt;/script&gt;
    &lt;script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;div id="app"&gt;&lt;/div&gt;
&lt;script src="demo.js" type="text/babel"&gt;&lt;/script&gt;
&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.7/react.js"&gt;&lt;/script&gt;
&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.14.7/react-dom.js"&gt;&lt;/script&gt;
&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.23/browser.min.js"&gt;&lt;/script&gt;
&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.1/jquery.min.js"&gt;&lt;/script&gt;
&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/marked/0.3.2/marked.min.js"&gt;&lt;/script&gt;
&lt;/body&gt;
&lt;/html&gt;</code></pre>
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