App.cable.subscriptions.create('DoneChannel', {
  received: function(data) {
    let c_id = '#done_' + data.done_id;
    let collection = $(c_id);
    collection.html(data.body);
  },
  connected: function() {
    console.log('done channel connected success');
  }
});

@@ -74,19 +74,19 @@
 ) %7B%0A    
-let
+var
  c_id = 
@@ -118,11 +118,11 @@
     
-let
+var
  col

the data