Disable browser backspace key (BACKSPACE) when jumping page (extjs,javascript)

Ext Implementation Method:

//Method OnevarKey =NewExt.keymap (document,{key:8, fn:function(obj,e) {varType =E.target.type; varReadOnly =e.target.readonly; if(Type! = ' text ' && type! = ' textarea ' && type! = ' Password '){    //E.preventdefault ();e.stopevent (); }   Else if(readonly) {//E.preventdefault ();e.stopevent (); }}, Scope: This });//Method TwoExt.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 (); }  }); 

How JavaScript is implemented:

function Document.onkeydown ()   {     if// mask backspace Delete key     {       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   ;   }}}

Disable browser backspace key (BACKSPACE) when jumping page (extjs,javascript)