JavaScript Examples ⁠-⁠ General edge functions on firewall example

    async function firewallHandler(event) {
        // Access the value of x-deny, one of the headers
        let condition = event.request.headers.get("x-deny");

        if (condition) {
            // event.deny() triggers a default 403 Response
            event.deny();
        }

        let anotherCondition = event.request.headers.get("x-drop"); // Access the value of x-drop, , one of the headers
        if (anotherCondition) {
            // event.drop() drops the connection without returning a Response
            event.drop();
        }

        // Access the value of x-third, one of the headers
        let aThirdCondition = event.request.headers.get("x-third");
        if (aThirdCondition) {
            // event.addRequestHeader() adds a new header to the Request object, passing key:"value".
            event.addRequestHeader("X-New-Request-Header", "Hello");
        }

        // Access the value of x-fourth, one of the headers
        let aFourthCondition = event.request.headers.get("x-fourth");
        if (aFourthCondition) {
            //  event.addResponseHeader() adds a new header to the Response object
            //  that will be delivered after accessing the origin.
            event.addResponseHeader("X-New-Response-Header", "Bye");
        }

        // The metadata object contains the attributes of the request
        if (event.request.metadata["remote_addr"] == "127.0.0.1") {
            // event.respondWith(new Response()) allows you to serve your own Response
            event.respondWith(new Response('{"my_custom_response": true}', {
                status: 599,
                headers: { "content-type": "application/json" }
            }));
        }

        // If the request was not denied or dropped and did not have a Response returned,
        // it is necessary to continue the processing, and to do so use use -> event.continue()
        // Do not forget this command, otherwise the request won't continue!
        event.continue();
    }

    addEventListener("firewall", (event) => event.waitUntil(firewallHandler(event)));