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Conditional response

Return a response based on the incoming request's URL, HTTP method, User Agent, IP address, ASN or device type.

const BLOCKED_HOSTNAMES = ["nope.mywebsite.com", "bye.website.com"]
async function handleRequest(request) {
// Return a new Response based on a URL's hostname
const url = new URL(request.url)
if (BLOCKED_HOSTNAMES.includes(url.hostname)) {
return new Response("Blocked Host", { status: 403 })
}
// Block paths ending in .doc or .xml based on the URL's file extension
const forbiddenExtRegExp = new RegExp(/\.(doc|xml)$/)
if (forbiddenExtRegExp.test(url.pathname)) {
return new Response("Blocked Extension", { status: 403 })
}
// On HTTP method
if (request.method === "POST") {
return new Response("Response for POST")
}
// On User Agent
const userAgent = request.headers.get("User-Agent") || ""
if (userAgent.includes("bot")) {
return new Response("Block User Agent containing bot", { status: 403 })
}
// On Client's IP address
const clientIP = request.headers.get("CF-Connecting-IP")
if (clientIP === "1.2.3.4") {
return new Response("Block the IP 1.2.3.4", { status: 403 })
}
// On ASN
if (request.cf && request.cf.asn == 64512) {
return new Response("Block the ASN 64512 response")
}
// On Device Type
// Requires Enterprise "CF-Device-Type Header" zone setting or
// Page Rule with "Cache By Device Type" setting applied.
const device = request.headers.get("CF-Device-Type")
if (device === "mobile") {
return Response.redirect("https://mobile.example.com")
}
console.error(
"Getting Client's IP address, device type, and ASN are not supported in playground. Must test on a live worker",
)
return fetch(request)
}
addEventListener("fetch", event => {
event.respondWith(handleRequest(event.request))
})