Deno Pokemon API

Today I wanted to dive a bit deeper into Deno and see how a very basic file API would look. Just to get a better feel for the Deno.

We are going to build a Pokémon API; We'll be able to do the following actions:

• Retrieve a list of all our Pokémon
• Catch a new Pokémon
• Level up a Pokémon
• Release a Pokémon back to the wild

Please note this uses local storage and is not connected to a Database!

Deno API

We will be using the oak module (see the Pokémon reference?) and import the Application and Router object:

import {Application, Router} from 'https://deno.land/x/oak/mod.ts';

Next up we start by defining our variables:

const env = Deno.env.toObject();
const PORT = env.PORT || 3000;
const HOST = env.HOST || '127.0.0.1';

Now we have to start our Oak application and run it.

// Define our router
const router = new Router();
// Define all our routes
router
  .get('/pokemon', getPokemons)
  .get('/pokemon/:name', getPokemon)
  .post('/pokemon', catchPokemon)
  .put('/pokemon/:name', levelUpPokemon)
  .delete('/pokemon/:name', releasePokemon);

// Define our application
const app = new Application();

// Tell the application to use our defined routes
app.use(router.routes());
// We do have to allow all methods since Deno is a secure environment
app.use(router.allowedMethods());

// And we'll start our app on the defined port and address
await app.listen(`${HOST}:${PORT}`);

That's our setup, but we now have to go and define all methods!

Deno Declaring our Interface

Before defining our methods, we have to declare our Pokémon interface and declare our basic Pokémons.

interface Pokemon {
  name: string;
  level: number;
}

let pokemons: Array<Pokemon> = [
  {
    name: 'Pikachu',
    level: 10
  },
  {
    name: 'Eevee',
    level: 50
  },
  {
    name: 'Snorlax',
    level: 20
  }
];

Awesome now we can start and build our methods, let's start by building our get function:

Deno Getting All Pokémon

GET: /pokemon

export const getPokemons = ({response}: {response: any}) => {
  response.body = pokemons;
};

Easy as that, on the request, we return the response of our Pokemon's, and it will look like this:

Deno Get Specific Pokémon

Ok, but what if we want to get one specific Pokémon based on their name?

GET: /pokemon/Pikachu

export const getPokemon = ({
  params,
  response
}: {
  params: {
    name: string
  },
  response: any
}) => {
  const pokemon = pokemons.filter(pokemon => pokemon.name === params.name);
  if (pokemon.length) {
    response.status = 200;
    response.body = pokemon[0];
    return;
  }

  response.status = 400;
  response.body = {msg: `Cannot find pokemon ${params.name}`};
};

Here we are listing to the params name and filter our Pokémons array. If none is, found we will return that we can't find the Pokémon.

Deno Catch a Pokémon

But we are proper Pokémasters, and we want to catch a Charizard!

POST: /pokemon

export const catchPokemon = async ({
  request,
  response
}: {
  request: any,
  response: any
}) => {
  const body = await request.body();
  const {name, level}: {name: string, level: number} = body.value;
  pokemons.push({
    name: name,
    level: level
  });

  response.body = {msg: 'OK'};
  response.status = 200;
};

We will post the name and level of the Pokémon, and that will add it to our local storage.

Deno Level Up a Pokémon

Ofcourse, we are very good trainers, and our Eevee is going to level up!

PUT: /pokemon/Eevee

export const levelUpPokemon = async ({
  params,
  request,
  response
}: {
  params: {
    name: string
  },
  request: any,
  response: any
}) => {
  const temp = pokemons.filter(pokemon => pokemon.name === params.name);
  const body = await request.body();
  const {level}: {level: number} = body.value;

  if (temp.length) {
    temp[0].level = level;
    response.status = 200;
    response.body = {msg: 'OK'};
    return;
  }

  response.status = 400;
  response.body = {msg: `Cannot find pokemon ${params.name}`};
};

Deno Releasing a Pokémon

There comes a time where you just have to let go off some Pokémon so let's release them back in the wild

DELETE /pokemon/snorlax

export const releasePokemon = ({
  params,
  response
}: {
  params: {
    name: string
  },
  response: any
}) => {
  const lengthBefore = pokemons.length;
  pokemons = pokemons.filter(pokemon => pokemon.name !== params.name);

  if (pokemons.length === lengthBefore) {
    response.status = 400;
    response.body = {msg: `Cannot find pokemon ${params.name}`};
    return;
  }

  response.body = {msg: 'OK'};
  response.status = 200;
};

I hope you found this tutorial useful!
You can find this project on GitHub.

Thank you for reading, and let's connect!

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