最少代码：HelloWorld.html源文件下载 

https://docs.sencha.com/extjs/6.7.0/classic/Ext.button.Button.html

点击 事件

<link  rel="stylesheet" href="theme-gray-all.css"><!--样式-->
<script src="ext-all.js"></script>   <!--行为-->
<script>Ext.onReady(function () { /*-自己写的代码--开始--ExtJS 入口,相当于Java/C的main函数-*/

  Ext.create('Ext.Button', {
     text: 'My Button',
    renderTo: Ext.getBody(),
    handler: function() {alert('click');}
  });
}); </script> <!--自己写的代码-----------------------结束------------------------>

 同时 ，点击，移开事件

Ext.create('Ext.Button', {
  text: 'My Button',
  renderTo: Ext.getBody(),
    listeners: {
              click: {    fn: function(){   alert('click'); }     },  //鼠标单击事件
           mouseout: {  fn: function(){  alert('Mouse out');      }   //鼠标移开事件
      }
 }
});

 创建一个带链接的按钮

Ext.create('Ext.Button', {
renderTo: Ext.getBody(),
text: 'Link Button',
href: 'http://www.baidu.com/'
});

 带下拉菜单的按钮

Ext.create('Ext.Button', {
text: 'My Button',
renderTo: Ext.getBody(),
menu: [{
               text: 'Item 1'}, {
               text: 'Item 2'}, {
               text: 'Item 3'
    }]
});

 Ext.Button has many other properties, such as bind, cls, disabled, html, tooltip, tpl, and so on, which you can use to customize the button.

Ext.create('Ext.Button', {
    text    : 'Dynamic Handler Button',
    renderTo: Ext.getBody(),
    handler : function() {
        // this button will spit out a different number every time you click it.
        // so firstly we must check if that number is already set:
        if (this.clickCountzz) {
            // looks like the property is already set, so lets just add 1 to that number
            // and alert the user
            this.clickCountzz++;
            alert('You have clicked the button "' + this.clickCountzz +
                  '" times.\n\nTry clicking it again..');
        } else {
            // if the clickCount property is not set, we will set it and alert the user
            this.clickCountzz = 1;
            alert('You just clicked the button for the first time!\n\n' +
                  'Try pressing it again..');
        }
    }
});