ReactFundamentals:UsingRefstoAccessComponents

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

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测试数据/ajax/libs/react/0.12.2/react.js"  >  script  > 
   script   src  ="https://cdnjs.cloudflare测试数据/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> {this.state.red}  /  label  >  br  /  > 
                        Silder update  =  {  this  .myUpdate} ref  =  "  green  "  >  /  Silder> {this.state.green}  /  label  >  br  /  > 
                        Silder update  =  {  this  .myUpdate} ref  =  "  blue  "  >  /  Silder> {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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