URLs and Paths

The server that we previously studied is a HTTP server that responds to HTTP requests. Each request is made to a specific URL, which also has a path.

Requested URL

The URL that has been requested can be accessed through the property url of the request-object. Running the following application launches a server that responds to the user with the URL that the request is made to.

const handleRequest = (request) => {
  return new Response(request.url);
};

Deno.serve(handleRequest);

We can test the printed URL either by using the browser or by using the curl command. In the following example, we first make a request to the root path of the server, i.e. to http://localhost:8000, after which make a request to the path /hello on the server, i.e. to http://localhost:8000/hello.

curl http://localhost:8000
http://localhost:8000/%
curl http://localhost:8000/hello
http://localhost:8000/hello%

In the above example where the curl command is run within a terminal, the percentage-sign % visible in the output depicts the lack of a line change at the end of the response. When trying out the request in a browser, no percentage sign is shown.

Requested paths

If we wish to use the path of the URL, e.g. /hello from http://localhost:8000/hello, we can use the URL-class to create an URL object out of the url variable representing the requested URL. The created object has properties through which we can access a variety of url parts, including the the path, which is stored in a property called pathname.

The example below launches a server that responds with the requested path.

const handleRequest = (request) => {
  const url = new URL(request.url);
  return new Response(url.pathname);
};

Deno.serve(handleRequest);

curl http://localhost:8000
/%
curl http://localhost:8000/hello
/hello%

Path-specific responses

Normally, when we make requests to different paths of websites, we get different responses. Let's mimic this behavior through a simple example.

The following example creates a server that responds with the message world to requests that are made to the path /hello and with the message ingredient to requests that are made to a path containing the string secret. Any other requests receive a response with the message hello.

const handleRequest = (request) => {
  const url = new URL(request.url);

  let message = "hello";
  if (url.pathname === "/hello") {
    message = "world";
  } else if (url.pathname.includes("secret")) {
    message = "ingredient";
  }

  return new Response(message);
};

Deno.serve(handleRequest);

We can, again, try out the application using the browser or the command line. In the following example, the application is tried out with a few curl requests.

curl http://localhost:8000
hello%
curl http://localhost:8000/world
hello%
curl http://localhost:8000/helloes
hello%
curl http://localhost:8000/hello
world%
curl http://localhost:8000/secret
ingredient%
curl http://localhost:8000/secrets
ingredient%