Checking for Duplicate values in a field

This section covers checking for duplicate values in a field.

To prevent users from uploading duplicate values for a specific field, you can utilize the data validation function.

Below is an example of such a function that identifies duplicate values in a column and displays an error message to the user:

      {
        name: "email address",
        displayName: "email address",
        description: "Email address of the user",
        validator: async (rows) => {
            let seen = {};
            return rows.map(row => {
                if (seen[row[2]]) {
                    return {
                        errorMessage: 'Duplicate value found. Please check.'
                    };
                }
                seen[row[2]] = true;
                return true;
            });
        }         
      }

In this function:

1. We iterate over each element in the rows array.

2. For each row, we check if the email address at index 2 (row[2]) has been seen before. If it has, we add it to the seen object.

3. After the loop, if any duplicate email addresses are found (i.e., if the seen object contains the email address more than once), we return an error message indicating the duplicate value found.

4. If no duplicate email addresses are found, we return true to indicate that the validation passed without any issues.