proxy.ts

/**
 * HTTP Proxy to arbitrary URL with Cloudflare Worker.
 */

/**
 * Cloudflare Worker entrypoint
 */
if (typeof addEventListener === 'function') {
    addEventListener('fetch', (e: Event): void => {
        // work around as strict typescript check doesn't allow e to be of type FetchEvent
        const fe = e as FetchEvent
        fe.respondWith(proxyRequest(fe.request))
    });
}

async function proxyRequest(r: Request): Promise<Response> {
    const url = new URL(r.url)
    const prefix = '/worker/proxy/'
    if (url.pathname.startsWith(prefix)) {
        const remainingUrl = url.pathname.replace(new RegExp('^' + prefix), '')
        let targetUrl = decodeURIComponent(remainingUrl)
        if (!targetUrl.startsWith('http://') && !targetUrl.startsWith('https://')) {
            targetUrl = url.protocol + '//' + targetUrl
        }
        return fetch(targetUrl)
    } else {
        return new Response('Bad Request', {status: 400, statusText: 'Bad Request'})
    }
}

interface FetchEvent extends Event {
    request: Request;

    respondWith(r: Promise<Response> | Response): Promise<Response>;
}