Hi,
It depends how the name is displayed in the lookup field – is it pulled from a free text field?
If it is 100% certain it is the same format as the “Display name” in the user info list you can use something like this in the custom js:
var ui = spjs.utility.userInfo(_spPageContextInfo.userId);
setFieldValue("Employee",ui.Title);
Let me know how this works out.
Alexander