Improved code
diff --git a/erpnext/hr/doctype/offer_letter/offer_letter.js b/erpnext/hr/doctype/offer_letter/offer_letter.js
index 552a9f0..526833a 100755
--- a/erpnext/hr/doctype/offer_letter/offer_letter.js
+++ b/erpnext/hr/doctype/offer_letter/offer_letter.js
@@ -1,6 +1,8 @@
 // Copyright (c) 2015, Frappe Technologies Pvt. Ltd. and Contributors
 // License: GNU General Public License v3. See license.txt
 
+frappe.provide("erpnext.offer_letter");
+
 frappe.ui.form.on("Offer Letter", {
 	select_terms: function(frm) {
 		frappe.model.get_value("Terms and Conditions", frm.doc.select_terms, "terms", function(value) {
@@ -10,16 +12,20 @@
 
 	refresh:function(frm){
 		if((!frm.doc.__islocal) && (frm.doc.status=='Accepted') && (frm.doc.docstatus===1)){
-		frm.add_custom_button(__('Make Employee'),
-		frm.cscript['Make Employee']);
-	}
-}
+			frm.add_custom_button(__('Make Employee'),
+				function() {
+					erpnext.offer_letter.make_employee(frm)
+				}
+			);
+		}
+	}		
+
 });
 
 
-cur_frm.cscript['Make Employee'] = function() {
-frappe.model.open_mapped_doc({
-	method: "erpnext.hr.doctype.employee.employee.make_employee",
-	frm : cur_frm
-});
+erpnext.offer_letter.make_employee = function(frm) { 
+	frappe.model.open_mapped_doc({
+		method: "erpnext.hr.doctype.employee.employee.make_employee",
+		frm : frm
+	});
 }
\ No newline at end of file