title: get class using Ext.get() in extjs
body: <p>Hello I am very  new to ExtJs please help me knowing Ext.get()</p>
  
  <p>This works:</p>
  
  <pre><code>  Ext.get('tag2').hide(); // worked well on with Id
     &lt;div id ="tag2"&gt;using id&lt;/div&gt;&lt;!--given with id--&gt;
  </code></pre>
  
  <p>Now this is the problem</p>
  
  <pre><code> Ext.get('tag2').hide()//hiding only id not class
   &lt;div class ="tag2"&gt;using class&lt;/div&gt;&lt;!--given with class--&gt;
  </code></pre>
  
  <p>Doesn't work on class. 
  Take a look the complete code:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
     &lt;head&gt;
        &lt;link href="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/classic/theme-neptune/resources/theme-neptune-all.css" rel="stylesheet" /&gt;
        &lt;script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/extjs/6.0.0/ext-all.js"&gt;&lt;/script&gt;
        &lt;script type="text/javascript"&gt;
           Ext.onReady(function(){
              Ext.get('tag2').hide()//hiding only id not class
              Ext.create('Ext.Button', {
                 renderTo: Ext.getElementById('helloWorldPanel'),
                 text: 'show',
                 listeners: {
                    click: function() {
                       this.hide();
                    },
                    hide: function() {
                       Ext.get('tag1').hide();
                       Ext.get('tag2').show();//not working hear
                    }
                 }
              });
           });           
        &lt;/script&gt; 
     &lt;/head&gt;
     &lt;body&gt;
     &lt;div class ="tag1"&gt;Test Div&lt;/div&gt;
     &lt;div class ="tag2"&gt;using class&lt;/div&gt;&lt;!--given with class--&gt;
     &lt;div id ="tag2"&gt;using id&lt;/div&gt;&lt;!--given with id--&gt;
     &lt;div id = 'helloWorldPanel' /&gt;   &lt;!--  panel will be rendered here-- &gt;
     &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>