update_change_handler.js

  changeHandler = event => {
    
    const name = event.target.name;
    const value = event.target.value;
    
    this.setState(prevState => {
      return {
        formControls: {
          ...prevState.formControls,
          [name]: {
            ...prevState.formControls[name],
            value: value
          }
        }
      }

    });
    
  }