refactoring, fix todo removal from lists

models/Todo.js

@@ -14,14 +14,22 @@ const TodoSchema = Schema({
 
 TodoSchema.pre('save', async function () {
   const list = await TodoList.findById(this.list);
-  list.todos.push(this.id);
+  list.todos.push(this._id);
   await list.save();
 });
 
 TodoSchema.pre('remove', async function () {
   const list = await TodoList.findById(this.list);
-  list.todos.remove(this.id);
+  list.todos.splice(list.todos.indexOf(this._id), 1);
   await list.save();
 });
 
+TodoSchema.methods.toJson = function () {
+  return {
+    id: this._id,
+    text: this.text,
+    list: this.list,
+  };
+};
+
 mongoose.model('Todo', TodoSchema);