If the built-in column types are not enough, you can define your own data structure using the String column. You do this through the use of onValidateRecord. You simply need to validate that the value passed to onValidateRecord matches your desired format.

​
Example of Creating a “Currency” Column

// matches formats like $10
const currencyRegex = /\$[0-9]*/;

const importer = new FuseImporter();

importer.getSessionToken = ... // see https://fuse-docs.flatirons.com/getting-started/sessions

importer.addColumn({
  internal_key: "total_charge",
  label: "Total Charge",
  column_type: "string",
  required: true,
  position: 1,
  unique: true,
});

importer.onValidateRecord = async (record) => {
  const errors = {};
  const warnings = {};

  // make sure the total charge matches the regex
  if (!record.total_charge?.match(currencyRegex)) {
    errors["total_charge"] =
      "Total charge must be a dollar amount matching the format $xx";
  }

  return {
    errors: errors,
    warnings: warnings,
  };
};

importer.show();