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Deno Web Development

Creating the Web Server

Explore how to create a configurable web server in Deno by writing a server function that accepts parameters through an interface. Learn to apply dependency inversion to inject business logic, enabling better testability and modularity. By the end, you will understand how to connect HTTP requests to your controller’s methods and verify your server's responses.

We'll cover the following...

Steps to create a server

Now that our functionality is in place, we need to expose it via a web server. Let’s use what we’ve learned from the standard library to create it by following these steps:

  1. Create a file named index.ts inside the src/web folder, and add the logic to create a server.
TypeScript 3.3.4
import { serve } from "https://deno.land/std@0.83.0/http/server.ts";
const PORT = 8080;
const server = serve({ port: PORT });
console.log(`Server running at https://localhost:${PORT}`);
for await (let req of server) {
    req.respond({ body: 'museums api', status: 200 })
}

Since we want our application to be easily configurable, we don’t want the port to be hardcoded here but to be configurable from the outside. We need to export this server creation logic as a function.

  1. Wrap the server logic creation inside a function that receives the configuration and port as an argument:
TypeScript 3.3.4
import { serve } from "https://deno.land/std@0.83.0/http/server.ts";
export async function createServer({
  configuration: {
    port
}
}) {
const server = serve({ port });
console.log(`Server running at http://localhost:${port}`);
for await (let req of server) {
  req.respond({ body: "museums api", status: 200 })
}
}

We’ll notice that the TypeScript compiler will warn us that we shouldn’t use the port defining its type.

  1. Make this function’s parameters an interface. This will help us in terms of documentation and will also add type safety and static checks:
TypeScript 3.3.4
interface CreateServerDependencies {
    configuration: {
        port: number
    }
}
export async function createServer({
    configuration: {
        port
}
}: CreateServerDependencies) {
...

Now that we have configured the web server, we can think of using it for our use case.

  1. Go back to src/index.ts, import createServer, and use it to create a server running on port 8080:
TypeScript 3.3.4
import { createServer } from "./web/index.ts";
...
createServer({
    configuration: {
    port: 8080
}
})
...

5. Run it and see if it works:

deno run --allow-net src/index.ts
run the index.ts file

Here, we can see that we have a log stating that the server is running:

Server running at 8080
Server running at 8080

Now, we can test ...