items[i]. itemThumbnail

Object containing details for the thumbnail of the first post for the blog.

items[i]. itemThumbnail is a member of the Blog List dictionary.

itemThumbnail has data type object

Objects are containers, which have named values of many items of data.

Objects can be constructed inline, using a squiggly-brace syntax similar to JSON.
Example: An inline object being passed to the string snippet operator.
<b:eval expr='snippet(data:post.body, { length: 150, links: false, linebreaks: false })' />