The first should work. A double-backslash should return as a single slash... the backslash character is used for escaping certain characters in JavaScript strings.
To verify, I created this little function.
function testSlash(){
var st;
st = 'TEST\\TESTS'; // Logs as 'TEST\TESTS'
Log.Message(st);
st = 'TEST\TESTS'; //Logs as 'TESTTESTS'
Log.Message(st);
}
So... my question for you... how are you using that string in your tests? What are you doing witih it? How are you consuming it? A bit more code context as to how you are determinng what is being returned would be helpful.