Script to create custom Pokemon data from the PokeAPI data at https://github.com/PokeAPI/api-data

createPokeData.js

// .../api-data/data/createPokeData.js
import { readdirSync, readFileSync, writeFileSync } from 'fs';
import { dirname, join } from 'path';
import { fileURLToPath } from 'url';

const baseDir = dirname(fileURLToPath(import.meta.url));

const pokemonDir = join(baseDir, 'api', 'v2', 'pokemon');
const outDir = join(baseDir, 'out');

// Filter function which will be used to get the `en` versions of all names and texts.
const findEn = (obj) => obj.language.name === 'en';

// Remove escape characters from a string
const unescape = (escapedStr) => escapedStr.replace(/[\u0000-\u001F\u007F-\u009F]/g, ' ').trim();

// Utility function to read the JSON file for the corresponding URL.
// URLs are of the format `/api/v2/{resource}/{index}/`
const readAsJson = (fileUrl) => {
    const fileContents = readFileSync(join(baseDir, fileUrl, 'index.json'), { encoding: 'utf-8' });
    return JSON.parse(fileContents);
};

const allPokemonDirs = readdirSync(pokemonDir, { withFileTypes: true });

let allPokemon = [];

for (const dir of allPokemonDirs) {
    if (dir.isDirectory()) {
        const pokemon = readAsJson(`api/v2/pokemon/${dir.name}`);

        // Basic species details
        const species = readAsJson(pokemon.species.url);
        const { name } = species.names.find(findEn);
        const { genus } = species.genera.find(findEn);
        const { flavor_text } = species.flavor_text_entries.find(findEn);
        const description = unescape(flavor_text);

        // Image URL
        const imageUrl = `https://raw.githubusercontent.com/anurag-roy/poke-api/main/assets/images/${pokemon.id}.webp`;

        // Types - Preserve slot order
        const types = pokemon.types
            .sort((t1, t2) => t1.slot - t2.slot)
            .map((t) => {
                const type = readAsJson(t.type.url);
                const { name } = type.names.find(findEn);
                return name;
            });

        // Abilities
        const abilities = pokemon.abilities.map((a) => {
            const ability = readAsJson(a.ability.url);
            const { name } = ability.names.find(findEn);
            let { effect } = ability.effect_entries.find(findEn) || {};
            effect = effect ? unescape(effect) : '';
            const { flavor_text } = ability.flavor_text_entries.find(findEn);
            const description = unescape(flavor_text);
            return {
                name,
                effect,
                description,
            };
        });

        // Stats
        const stats = pokemon.stats.reduce((statsObj, currentStat) => {
            const stat = readAsJson(currentStat.stat.url);
            const { name } = stat.names.find(findEn);
            statsObj[name] = currentStat.base_stat;
            return statsObj;
        }, {});

        // Encounters and locations
        const encounters = readAsJson(pokemon.location_area_encounters);
        const locations = encounters.map((e) => {
            const locationArea = readAsJson(e.location_area.url);
            const location = readAsJson(locationArea.location.url);
            const { name } = location.names.find(findEn);
            return name;
        });
        const uniqueLocations = Array.from(new Set(locations));

        // Construct final object
        const outputPokemon = {
            id: pokemon.id,
            name,
            genus,
            description,
            imageUrl,
            types,
        };

        allPokemon.push(outputPokemon);

        // Slightly more detailed object
        const pokemonDetail = {
            ...outputPokemon,
            abilities,
            stats,
            locations: uniqueLocations,
        };

        writeFileSync(`${outDir}/${dir.name}.json`, JSON.stringify(pokemonDetail), {
            encoding: 'utf-8',
        });
    }
}

// Sort to order pokemon as 1,2,3,.. instead of 1,10,100,...
allPokemon = allPokemon.sort((p1, p2) => p1.id - p2.id);

writeFileSync(`${outDir}/pokemon.json`, JSON.stringify(allPokemon), {
    encoding: 'utf-8',
});