worker-index.js

import { getAssetFromKV, mapRequestToAsset } from '@cloudflare/kv-asset-handler'

/**
 * The DEBUG flag will do two things that help during development:
 * 1. we will skip caching on the edge, which makes it easier to
 *    debug.
 * 2. we will return an error message on exception in your Response rather
 *    than the default 404.html page.
 */
const DEBUG = false

addEventListener('fetch', event => {
    try {
        event.respondWith(handleEvent(event))
    } catch (e) {
        if (DEBUG) {
            return event.respondWith(
                new Response(e.message || e.toString(), {
                    status: 500,
                }),
            )
        }
        event.respondWith(new Response('Internal Error', { status: 500 }))
    }
})

async function handleEvent(event) {
    const url = new URL(event.request.url)
    let options = {}

    /**
     * You can add custom logic to how we fetch your assets
     * by configuring the function `mapRequestToAsset`
     */
    // options.mapRequestToAsset = handlePrefix(/^\/docs/)

    try {
        if (DEBUG) {
            // customize caching
            options.cacheControl = {
                bypassCache: true,
            };
        }
        const page = await getAssetFromKV(event, options);

        // allow headers to be altered
        const response = new Response(page.body, page);

        response.headers.set("X-XSS-Protection", "1; mode=block");
        response.headers.set("X-Content-Type-Options", "nosniff");
        response.headers.set("X-Frame-Options", "DENY");
        response.headers.set("Referrer-Policy", "unsafe-url");
        response.headers.set("Feature-Policy", "none");
        response.headers.set("Cache-Control", "max-age=31536000");

        return response;

    } catch (e) {
        // if an error is thrown try to serve the asset at 404.html
        
        if (!DEBUG) {
            try {
                let notFoundResponse = await getAssetFromKV(event, {
                    mapRequestToAsset: req => new Request(`${new URL(req.url).origin}/404.html`, req),
                })

                return new Response(notFoundResponse.body, { ...notFoundResponse, status: 404 })
            } catch (e) {}
        }

        return new Response(e.message || e.toString(), { status: 500 })
    }
}

/**
 * Here's one example of how to modify a request to
 * remove a specific prefix, in this case `/docs` from
 * the url. This can be useful if you are deploying to a
 * route on a zone, or if you only want your static content
 * to exist at a specific path.
 */
function handlePrefix(prefix) {
    return request => {
        // compute the default (e.g. / -> index.html)
        let defaultAssetKey = mapRequestToAsset(request)
        let url = new URL(defaultAssetKey.url)

        // strip the prefix from the path for lookup
        url.pathname = url.pathname.replace(prefix, '/')

        // inherit all other props from the default request
        return new Request(url.toString(), defaultAssetKey)
    }
}