@olenbetong/data-binding/src/form.js

function stringToNumber(value) {
  if (!value) {
    return value;
  }

  if (typeof value === "string") {
    value = value.replace(",", ".");
    value = value.replace("−", "-");
    value = Number(value);
  }

  return value;
}

function getFormValue(value, type) {
  if (value === "") {
    return null;
  } else if (type === "number") {
    let numValue = stringToNumber(value);

    return isNaN(numValue) ? undefined : numValue;
  } else if (["date", "datetime"].includes(type)) {
    let dateValue = new Date(value);

    return isNaN(dateValue.getTime()) ? undefined : dateValue;
  } else if (type === "boolean") {
    return value.toLowerCase() === "true";
  }

  return value;
}

export function formDataToObject(form, typeMap = {}) {
  let formData = new FormData(form);
  let result = new Map();

  for (let [field, value] of formData.entries()) {
    let type = typeMap?.[field] ?? "string";
    value = getFormValue(value, type);

    if (result.has(field)) {
      let current = result.get(field);

      if (Array.isArray(current)) {
        current.push(value);
      } else {
        result.set(field, [current, value]);
      }
    } else {
      result.set(field, value);
    }
  }

  return Object.fromEntries(result);
}

export function formDataToProcedureParameters(form, procedure) {
  let parameters = procedure.getParameters();
  let types = Object.fromEntries(parameters.map(param => [param.name, param.type]));

  return formDataToObject(form, types);
}