static-cms/website/content/docs/customization.md

---
title: Creating Custom Previews
weight: 50
group: Customization
---

The Static CMS exposes a `window.CMS` global object that you can use to register custom widgets, previews and editor plugins. The available customization methods are:

- **registerPreviewTemplate:** Registers a template for a collection.

### React Components inline interaction

Static CMS is a collection of React components and exposes two constructs globally to allow you to create components inline: ‘createClass’ and ‘h’ (alias for React.createElement).

## `registerPreviewTemplate`

Registers a template for a folder collection or an individual file in a file collection.

`CMS.registerPreviewTemplate(name, react_component);`

**Params:**

- name: The name of the collection (or file for file collections) which this preview component will be used for.
  - Folder collections: Use the name of the collection
  - File collections: Use the name of the file
- react_component: A React component that renders the collection data. Six props will be passed to your component during render:

  - entry: Immutable collection containing the entry data.
  - widgetFor: Returns the appropriate widget preview component for a given field.
  - [widgetsFor](#lists-and-objects): Returns an array of objects with widgets and associated field data. For use with list and object type entries.
  - getAsset: Returns the correct filePath or in-memory preview for uploaded images.
    **Example:**

    ```html
    <script src="https://unpkg.com/@staticcms/core@%5E0.1.0/dist/static-cms-core.js"></script>
    <script>
      var PostPreview = createClass({
        render: function () {
          var entry = this.props.entry;
          var image = entry.data.image;
          var bg = this.props.getAsset(image);
          return h(
            'div',
            {},
            h('h1', {}, entry.data.title),
            h('img', { src: bg.toString() }),
            h('div', { className: 'text' }, this.props.widgetFor('body')),
          );
        },
      });

      CMS.registerPreviewTemplate('posts', PostPreview);
    </script>
    ```

  - document: The preview pane iframe's [document instance](https://github.com/ryanseddon/react-frame-component/tree/9f8f06e1d3fc40da7122f0a57c62f7dec306e6cb#accessing-the-iframes-window-and-document).
  - window: The preview pane iframe's [window instance](https://github.com/ryanseddon/react-frame-component/tree/9f8f06e1d3fc40da7122f0a57c62f7dec306e6cb#accessing-the-iframes-window-and-document).

  ### Lists and Objects

  The API for accessing the individual fields of list- and object-type entries is similar to the API for accessing fields in standard entries, but there are a few key differences. Access to these nested fields is facilitated through the `widgetsFor` function, which is passed to the preview template component during render.
  **Note**: as is often the case with the Static CMS API, arrays and objects are created with Immutable.js. If some of the methods that we use are unfamiliar, such as `getIn`, check out [their docs](https://facebook.github.io/immutable-js/docs/#/) to get a better understanding.
  **List Example:**

  ```html
  <script>
    var AuthorsPreview = createClass({
      // For list fields, the widgetFor function returns an array of objects
      // that you can map over in your template. If our field is a list of
      // authors containing two entries, with fields `name` and `description`,
      // the return value of `widgetsFor` would look like this:
      //
      // [{
      //   data: { name: 'Mathias', description: 'Co-Founder'},
      //   widgets: { name: (<WidgetComponent>), description: (WidgetComponent>)}
      // },
      // {
      //   data: { name: 'Chris', description: 'Co-Founder'},
      //   widgets: { name: (<WidgetComponent>), description: (WidgetComponent>)}
      // }]
      //
      // Templating would look something like this:

      render: function () {
        return h(
          'div',
          {},

          // This is a static header that would only be rendered once for the entire list
          h('h1', {}, 'Authors'),

          // Here we provide a simple mapping function that will be applied to each
          // object in the array of authors
          this.props.widgetsFor('authors').map(function (author, index) {
            return h(
              'div',
              { key: index },
              h('hr', {}),
              h('strong', {}, author.data.name),
              author.widgets.description,
            );
          }),
        );
      },
    });
    CMS.registerPreviewTemplate('authors', AuthorsPreview);
  </script>
  ```

  **Object Example:**

  ```html
  <script>
    var GeneralPreview = createClass({
      // Object fields are simpler than lists - instead of `widgetsFor` returning
      // an array of objects, it returns a single object. Accessing the shape of
      // that object is the same as the shape of objects returned for list fields:
      //
      // {
      //   data: { front_limit: 0, author: 'Chris' },
      //   widgets: { front_limit: (<WidgetComponent>), author: (WidgetComponent>)}
      // }
      render: function () {
        var entry = this.props.entry;
        var title = entry.data.site_title;
        var posts = entry.data.posts;

        return h(
          'div',
          {},
          h('h1', {}, title),
          h(
            'dl',
            {},
            h('dt', {}, 'Posts on Frontpage'),
            h('dd', {}, this.props.widgetsFor('posts').widgets.front_limit || 0),

            h('dt', {}, 'Default Author'),
            h('dd', {}, this.props.widgetsFor('posts').data.author || 'None'),
          ),
        );
      },
    });

    CMS.registerPreviewTemplate('general', GeneralPreview);
  </script>
  ```