object_to_form_data.js

function getProperties(prefix, obj) {
  if (obj === null || obj === undefined) {
    return [];
  }

  if (obj instanceof Blob || obj instanceof File) {
    return [{ name: prefix, value: obj }];
  }

  if (typeof obj !== 'object') {
    return [{ name: prefix, value: obj.toString() }];
  }

  const properties = [];

  Object.keys(obj).forEach(key => {
    const value = obj[key], name = `${prefix}[${key}]`;

    if (Array.isArray(value)) {
      value.forEach(arrItem => properties.push(...getProperties(name + '[]', arrItem)));
    }
    else {
      properties.push(...getProperties(name, value));
    }
  })

  return properties;
}

function toFormData(prefix, obj) {
  const formData = new FormData();

  getProperties(prefix, obj).forEach(({ name, value }) => formData.append(name, value));

  return formData;
}

const formData = toFormData('profile', data);