Show unsupported message for old browsers

frappe/public/js/frappe/desk.js

@@ -10,6 +10,13 @@ frappe.start_app = function() {
 }
 
 $(document).ready(function() {
+	if(!frappe.utils.supportsES6) {
+		frappe.msgprint({
+			indicator: 'red',
+			title: __('Browser not supported'),
+			message: __('Some of the features might not work in your browser. Please update your browser to the latest version.')
+		});
+	}
 	frappe.start_app();
 });
 
@@ -133,9 +140,9 @@ frappe.Application = Class.extend({
 				var s = new frappe.ui.Dialog({
 						title: __("Checking one moment"),
 					fields: [{
-                    "fieldtype": "HTML",
-                    "fieldname": "checking"
-                }]
+					"fieldtype": "HTML",
+					"fieldname": "checking"
+				}]
 					});
 				s.fields_dict.checking.$wrapper.html('<i class="fa fa-spinner fa-spin fa-4x"></i>')
 				s.show();
@@ -415,10 +422,10 @@ frappe.Application = Class.extend({
 		if(window.mixpanel) {
 			window.mixpanel.identify(frappe.session.user);
 			window.mixpanel.people.set({
-			    "$first_name": frappe.boot.user.first_name,
-			    "$last_name": frappe.boot.user.last_name,
-			    "$created": frappe.boot.user.creation,
-			    "$email": frappe.session.user
+				"$first_name": frappe.boot.user.first_name,
+				"$last_name": frappe.boot.user.last_name,
+				"$created": frappe.boot.user.creation,
+				"$email": frappe.session.user
 			});
 		}
 	},

frappe/public/js/frappe/misc/utils.js

@@ -573,7 +573,16 @@ frappe.utils = {
 		});
 
 		return email_list;
-	}
+	},
+	supportsES6: function() {
+		try {
+			new Function("(a = 0) => a");
+			return true;
+		}
+		catch (err) {
+			return false;
+		}
+	}()
 };
 
 // String.prototype.includes polyfill