vfile VS unist-util-visit

file (required): a virtual file format.

Although we are building a custom table of contents, we won't have to write everything from scratch. To separate the Markdown/MDX content from the front matter, we'll use the Gray-matter package. It is optional in case you don't have front matter in your Markdown files. To process the Markdown itself, we'll use the Remark package. We'll also need the unist-util-visit package for traversing node trees and mdast-util-to-string for getting the text content of a node.

For this example, we will use unist-util-visit to recursively inspect all the image nodes, and unist-util-generated to ensure we are not inspecting nodes that we have generated ourselves and do not belong to the doc.md.