Solve the problem of clicking backspace to return to the previous page

The code is as follows:
/**
*
* It is forbidden to click backspace to return to the previous page
*/
window.onload=function(){
document.getElementsByTagName("body")[0].onkeydown =function(){
                                                                                                                                                                                  The code ELEM = EVENT.RELELATEDTARGET || Event.srcelement || Event.target || Event.currenttarget; Time label Make the pointed element
            var elem = event.srcElement                                                                var name = elem.nodeName;
                                           && name!='TEXTAREA'){                                                                                                                                                                                                 If(name=='INPUT' && (type_e!='TEXT' && type_e! ='TEXTAREA' && type_e!='PASSWORD' && type_e!='FILE')){                                                                                                                                                                      NPUT' && (elem.readOnly==true || elem .disabled == True) {
Return_Stopit (Event);

if (



e.preventDefault ){