Replace / with \ in processflow?

I am retrieving the PRTFILEPATH field from the USERRPT table.  The field value looks like:

E:\lsfprod\law/print/userid/po120abc/1

It has a combination of \ and /.  When I use the value in a command, the syntax comes back as invalid.  

I am trying to use the javascript .replace method.  It replaces any character I specify - except /.  

Can someone tell me the correct syntax for the following (assuming where p is specified it should be / and where X is specified it should be \)?:

var str = RtvUSERRPT_PRTFILEPATH;
var res = str.replace(/p/g, "X");

Thank you