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Responses ​

An overview of SPF responses and how they are processed.

In dynamic navigation, SPF updates the page with content from the response. Processing happens in a fixed order:

title → url → head → attr → body → foot

StepEffect
titleUpdates document.title
urlRewrites the current history entry to the correct URL
headInstalls early CSS/JS into <head>
attrSets attributes on elements by ID
bodyReplaces each fragment's content by ID
footInstalls late JS/CSS after the body

All fields are optional; the commonly needed ones are title, head, body, and foot.

Single response ​

A response is typically a single JSON object:

json
{
  "title": "Page Title",
  "head": "<style>…</style>",
  "body": { "content": "<p>New content</p>" },
  "foot": "<script>…</script>"
}
  • head — early CSS/JS, installed into <head>;
  • body — { "elementId": "HTML" }, replaces each element's content;
  • foot — late JS/CSS, installed after the body.

This follows the general good practice of "styles in the head, scripts at the end of the body". The foot field represents the "end of the body" section without requiring developers to create an explicit element.

Updating attributes ​

To update element attributes instead of content:

json
{
  "attr": {
    "content": { "class": "wide", "aria-busy": "false" }
  }
}

Beyond the basics ​

  • Streaming — a server may answer with an NDJSON stream of parts instead of one JSON object, processed as they arrive; see Multipart responses.
  • Caching hints — cacheKey and cacheType let the server address and classify entries in the response cache; see Caching.
  • Failure — reload: true forces a full browser navigation; redirect falls back to a full navigation of the target URL.

See the wire protocol for the exact byte-level contract (identifier, headers, streaming) and the Types reference for the SingleResponse shape.