禁止浏览器backspace键(退格键)时跳转页面（extjs,javascript）详解编程语言

//方法一 
 var key = new Ext.KeyMap(document,{ 
  key: 8, 
  fn: function(obj,e){ 
   var type = e.target.type; 
   var readonly = e.target.readOnly; 
   if(type != 'text' && type != 'textarea' && type != 'password'){ 
    //e.preventDefault(); 
    e.stopEvent(); 
   } 
   else if(readonly){ 
    //e.preventDefault(); 
    e.stopEvent(); 
   } 
  }, 
  scope: this 
 }); 
//方法二 
 
 
 
Ext.getDoc().on('keydown',function(e){   
    if(e.getKey() == 8 && e.getTarget().type =='text' && !e.getTarget().readOnly){   
           
    }else if(e.getKey() == 8 && e.getTarget().type =='textarea' && !e.getTarget().readOnly){    
       
    }else if(e.getKey() == 8){   
        e.preventDefault();   
    }   
}); 

function document.onkeydown()    
{    
  if ((event.keyCode==8) ) //屏蔽退格删除键   
  {    
    if (window.event.srcElement.tagName.toUpperCase()!="INPUT" && window.event.srcElement.tagName.toUpperCase()!="TEXTAREA" && window.event.srcElement.tagName.toUpperCase()!="TEXT")   
    {   
      event.keyCode=0;    
      event.returnValue=false;   
    }    
  }    
}