Subscribe

Deno Pokemon API

✍️

Building a basic Pokémon API in Deno

9 Aug, 2020 · 5 min read

Today I wanted to dive deeper into Deno and see how a fundamental file API would look. 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 must declare our Pokémon interface and basic Pokémons.

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

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

Extraordinary now, we can start and build our methods. Let's start by making 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, and it will look like this:

Get all Pokémon

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 filtering our Pokémons array. If none is found, we will return that we can't find the Pokémon.

Get single 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 to add it to our local storage.

Catch Pokémon

Deno Level Up a Pokémon

Of course, we are perfect trainers, and our Eevee will 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}` };
};

Pokémon level up

Deno Releasing a Pokémon

There comes a time when you must let go of some Pokémon to 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;
};

Release Pokémon

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

Thank you for reading, and let's connect!

Thank you for reading my blog. Feel free to subscribe to my email newsletter and connect on Facebook or Twitter

Spread the knowledge with fellow developers on Twitter
Tweet this tip
Powered by Webmentions - Learn more

Read next 📖

Deno Render HTML with view engine and ejs

11 Aug, 2020 · 2 min read

Deno Render HTML with view engine and ejs

Getting Started with Deno 🦕

6 Aug, 2020 · 2 min read

Getting Started with Deno 🦕

Join 1832 devs and subscribe to my newsletter