import { buildClient } from '@datocms/cma-client-node';
async function run() {
  const client = buildClient({ apiToken: '<YOUR_API_TOKEN>' });
  
  const fieldIdOrApiKey = 'blog_post::title';
  
  const field = await client.fields.update(fieldIdOrApiKey, {
    default_value: {
      en: 'A default value',
      it: 'Un valore di default'
    },
    label: 'Title',
    api_key: 'title',
    localized: true,
    validators: {
      required: {}
    },
    appearance: {
      editor: 'single_line',
      parameters: {
        heading: false
      },
      addons: [
        {
          id: '1234',
          field_extension: 'lorem_ipsum',
          parameters: {}
        }
      ]
    },
    position: 1,
    field_type: 'string',
    hint: 'This field will be used as post title',
    fieldset: null
  });
  
  console.log(field);
}
run();

{
  id: '124',
  label: 'Title',
  field_type: 'string',
  localized: true,
  default_value: {
    en: 'A default value',
    it: 'Un valore di default'
  },
  api_key: 'title',
  hint: 'This field will be used as post title',
  validators: {
    required: {}
  },
  appearance: {
    editor: 'single_line',
    parameters: {
      heading: false
    },
    addons: [
      {
        id: '1234',
        field_extension: 'lorem_ipsum',
        parameters: {}
      }
    ]
  },
  position: 1,
  item_type: {
    type: 'item_type',
    id: '44'
  },
  fieldset: null
}