When you are using React components you need to be able to access specific references to individual components. This is done by defining a ref.

<!DOCTYPE html>

<html>

<head lang="en">

    <meta charset="UTF-8">

    <title>React Lesson 5: Using Refs to Access Components</title>

</head>

<body>

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.12.2/react.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/0.12.2/JSXTransformer.js"></script>

<script type="text/jsx">

    var React_app = React.createClass({

        getInitialState: function() {

            return {

                red: 128,

                green: 128,

                blue: 128

            }

        },

        myUpdate: function(){

            this.setState({

                red: this.refs.red.getDOMNode().value,

                green: this.refs.green.getDOMNode().value,

                blue: this.refs.blue.getDOMNode().value

            });

        },

        render: function() {

            return (

                 <div>

                     <Silder update={this.myUpdate} ref="red"></Silder><label>{this.state.red}</label><br/>

                     <Silder update={this.myUpdate} ref="green"></Silder><label>{this.state.green}</label><br/>

                     <Silder update={this.myUpdate} ref="blue"></Silder><label>{this.state.blue}</label><br/>

                 </div>

            );

        }

    });

    var Silder = React.createClass({

        render: function(){

            return (

                 <input type="range" min="0" max="255"  onChange={this.props.update}/>

            )

        }

    });

    React.render(<React_app />, document.body);

</script>

</body>

</html>

Here we use getDOMNode() to get the html node:

 <Silder update={this.myUpdate} ref="red"></Silder>

then get value from it:

this.refs.red.getDOMNode().value

But, if we add a div:

    var Silder = React.createClass({

        render: function(){

            return (

               <div>  <!--  added  -->

                 <input type="range" min="0" max="255"  onChange={this.props.update}/>

               </div>  <!--  added  -->

            )

        }

    });

We found it doesn't work.

The way can solve this problem is by adding another ref to the input element:

    var Silder = React.createClass({

        render: function(){

            return (

               <div >

                 <input type="range" min="0" max="255" ref="range" onChange={this.props.update}/>

               </div>

            )

        }

    });
        myUpdate: function(){

            this.setState({

                red: this.refs.red.refs.range.getDOMNode().value,

                green: this.refs.green.refs.range.getDOMNode().value,

                blue: this.refs.blue.refs.range.getDOMNode().value

            });

        },

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