Page data

Every page has one data object, exposed as `page` in JSX and Go templates and
returned for each page by `pages()`. Frontmatter, `data()` calls, defaults, and
taragen's own keys all write into this same object.

## Where data comes from

Data is filled in this order, and later writers win:

1. Taragen seeds `path` and `slug` (and `params` for generated pages), and sets
   `outputs`.
2. `_defaults.jsx` files, from the site root down to the page's folder.
3. The page itself: YAML frontmatter in Markdown and templates, or `data({...})`
   in JSX.
4. Layouts, while rendering: frontmatter in template layouts, `data()` in JSX
   layouts.

After every page is parsed, taragen sets `links` and `backlinks` on every page.

## Built-in keys

Any key you set that isn't listed here is yours: `title`, `description`, `tags`,
and so on flow through untouched. These keys have built-in meaning:

| Key | Set by | Meaning |
| --- | --- | --- |
| `path` | taragen | The page's URL path, such as `/articles/2021/ngrok`. |
| `slug` | taragen | The last segment of the path, such as `ngrok`. |
| `src` | taragen | The raw page source (for generated pages, the template's source). |
| `body` | taragen | The page's rendered body, before layouts. |
| `isDir` | taragen | True for folders and `index.*` files. |
| `subpages` | taragen | In `pages()` results: the page's children, sorted, each with its own `subpages`. |
| `params` | taragen | Generated pages only: the parameter values, such as `{ year: "2026", month: "11" }`. |
| `outputs` | you, then taragen | You set it to turn outputs off; taragen replaces it with a map of output name to URL. See [Extra outputs per page](/docs/manual/extra-outputs-per-page). |
| `links` | taragen | Sorted list of the site pages this page's body links to. |
| `backlinks` | taragen | Pages whose bodies link to this page. See [Backlinks](/docs/manual/backlinks). |
| `aliases` | you | Old URLs that redirect to this page. Taragen replaces it with the normalized list. See [Aliases and redirects](/docs/manual/aliases-and-redirects). |
| `siteURL` | you | The site's absolute origin, such as `https://example.com`. Used to recognize absolute links to your own pages, and handy for building absolute URLs in feeds and meta tags. |
| `layout` | you | Layout path to use instead of the folder layouts, such as `_blog/_layout`. `""` turns layouts off. |
| `date` | you | `YYYY-MM-DD`. Orders listings; a future date makes the page a draft. |
| `draft` | you | `true` makes the page a draft. |
| `contentType` | you | The HTTP `Content-Type` in `serve`. Defaults to `text/html`. |
| `preamble` | you | Text written before the output. Defaults to `<!DOCTYPE html>` for HTML. |

Keys set by taragen replace whatever a page sets for them. Avoid using `outputs`,
`links`, `backlinks`, `aliases`, or `params` for your own data.