@work-bee/precache-json

Extracts a precache route manifest from a JSON response, for use as precache.extract in @work-bee/core.

@work-bee/core deliberately ships no default extractor: the shape of a route manifest is an application concern, so parsing it is a plugin rather than something baked into the core bundle. When precache.routes is a URL, core requires an explicit extract.

Install

npm install @work-bee/precache-json

Usage

import { compileConfig, eventInstall, strategyCacheFirst } from "@work-bee/core";
import { precacheExtractJSON } from "@work-bee/precache-json";

const config = compileConfig({
  precache: {
    routes: "/precache.json",
    extract: precacheExtractJSON,
  },
  strategy: strategyCacheFirst,
});

addEventListener("install", (event) => {
  eventInstall(event, config);
});

Where /precache.json serves an array of routes:

[{ "path": "/index.html" }, { "path": "/app.css" }, { "path": "/app.js" }]

Entries may be plain strings or route objects; both are compiled through the same route pipeline as inline precache.routes.

Behaviour

precacheExtractJSON(response) returns Promise<Route[]>.

Response	Result
Content-Type: application/json (any parameters, e.g. ; charset=utf-8) with an array body	the parsed array
Any other Content-Type, or no Content-Type	[] — nothing is precached
application/json with a non-array body	throws TypeError naming the received type

The media type is matched by prefix on the type/subtype only, after trimming and lowercasing, so application/json5 also matches.

Writing your own

extract is any (response) => Route[] | Promise<Route[]>. To read a manifest in another format, pass your own:

const config = compileConfig({
  precache: {
    routes: "/precache.txt",
    extract: async (response) =>
      (await response.text()).split("\n").filter(Boolean),
  },
});

License

Licensed under MIT License. Copyright (c) 2026 will Farrell and the Workbee contributors.