Solve the Problem of clicking backspace and returning to the previous page

Do not click backspace to return to the previous page * window. onloadfunction () {document. getElementsByTagName (& amp; quot; body & amp; quot;) [0]. onkeydownfunction (){... the Code is as follows:
/**
*
* Do not click backspace to return to the previous page.
*/
Window. onload = function (){
Document. getElementsByTagName ("body") [0]. onkeydown = function (){

// Obtain the event object
Var elem = event. relatedTarget | event. srcElement | event.tar get | event. currentTarget;

If (event. keyCode = 8) {// judge that the key is the backSpace key.

// Obtain the element pointed to by pressing the time mark on the key.
Var elem = event. srcElement | event. currentTarget;

// Determine whether to prevent the default transfer of events that press the keyboard
Var name = elem. nodeName;

If (name! = 'Input' & name! = 'Textea '){
Return _ stopIt (event );
}
Var type_e = elem. type. toUpperCase ();
If (name = 'input' & (type_e! = 'Text' & type_e! = 'Textea '& type_e! = 'Password' & type_e! = 'File ')){
Return _ stopIt (event );
}
If (name = 'input' & (elem. readOnly = true | elem. disabled = true )){
Return _ stopIt (event );
}
}
}
}
Function _ stopIt (e ){
If (e. returnValue ){
E. returnValue = false;
}
If (e. preventDefault ){
E. preventDefault ();
}

Return false;
}