ReactJS – Function to bulk overwrite nested usestate variable

January 30, 2022

I have a nested dictionary object with the following structure:

  const [fieldErrorMessage, setFieldErrorMessage] = useState({
    signinEmail: {
      show: false,
      message: "Error",
    },
    signinPassword: {
      show: false,
      message: "Error",
    },
    signupEmail: {
      show: false,
      message: "Error",
    },
    signupPassword: {
      show: false,
      message: "Error",
    },
    signupRegistrationToken: {
      show: false,
      message: "Error",
    },
  });

I created a function which should take in an array of nested dictionaries (e.g., signinEmail, signinPassword, …) and set their value for their show key to false (without changing the value for the message property).

Here is my function:

function hideFieldErrors(setter, fieldNameArray) {
  fieldNameArray.forEach((fieldName) => {
    setter((prevState) => ({
      ...prevState,
      fieldName: {
        ...prevState.fieldName,
        show: false,
      },
    }));
  });
}

When I call it, the show values do not change. Why is that?

I’m calling it via this code:

hideFieldErrors(setFieldErrorMessage, [
    "signinEmail",
    "signinPassword",
    "signupEmail",
    "signupPassword",
    "signupRegistrationToken",
  ]);

>Solution :

The way you have used fieldName is not working as you expected. variable name(which is a string) should be wrapped with square brackets to make it an accessible property.

Try like below.

function hideFieldErrors(setter, fieldNameArray) {
  fieldNameArray.forEach((fieldName) => {
    setter((prevState) => ({
      ...prevState,
      [fieldName]: {
        ...prevState[fieldName],
        show: false,
      },
    }));
  });
}