src/app/App.js
/* 
  = callback function =
  this function gets passed into <TodoForm /> and is called by its onSubmit handler;
  allows us to update the `todos` state with the input entered in the text field
  */
callback function
this function gets passed into  and is called by its onSubmit handler;
allows us to update the `todos` state with the input entered in the text field
callback function this function gets passed into and is called by its onSubmit handler ; allows us to update the ` todos ` state with the input entered in the text field
handleFormSubmit(value) {
    const newTodo = { value: value, id: index }
    let newTodos = this.state.todos.concat([newTodo]);
    this.setState({ todos: newTodos });
    index++;
  }
handleFormSubmit ( value ) { const newTodo = { value : value , id : index } let newTodos = this . state . todos . concat ( [ newTodo ] ) ; this . setState ( { todos : newTodos } ) ; index ++ ; }
callback function
this function gets passed into <TodoForm /> and is called by its onSubmit handler;
allows us to update the `todos` state with the input entered in the text field
callback function this function gets passed into <TodoForm / > and is called by its onSubmit handler ; allows us to update the ` todos ` state with the input entered in the text field