1 files changed, 58 insertions, 0 deletions
diff --git a/js/poke-chain.js b/js/poke-chain.js
new file mode 100644
index 0000000..2e227b6
--- /dev/null
+++ b/js/poke-chain.js
@@ -0,0 +1,58 @@
+const API_BASE = "https://pokeapi.co/api/v2";
+
+/**
+ * Fetches JSON data from a given URL.
+ * @param {string} url 
+ * @returns {Promise<any>}
+ */
+const fetchJSON = (url) => 
+  fetch(url).then((res) => res.ok ? res.json() : Promise.reject(`Error: ${res.status}`));
+
+/**
+ * Fetches a Pokémon's species data to get the evolution chain URL.
+ * @param {string|number} identifier - Pokémon name or ID.
+ * @returns {Promise<string>}
+ */
+const getEvolutionChainUrl = (identifier) =>
+  fetchJSON(`${API_BASE}/pokemon-species/${identifier}`)
+    .then((data) => data.evolution_chain.url);
+
+/**
+ * Fetches and extracts evolution chain details.
+ * @param {string} url - Evolution chain API URL.
+ * @returns {Promise<string[]>} - Evolution chain sequence.
+ */
+const getEvolutionChain = (url) => 
+  fetchJSON(url).then((data) => extractEvolutionChain(data.chain));
+
+/**
+ * Recursively extracts evolution names from chain data.
+ * @param {Object} chain 
+ * @returns {string[]}
+ */
+const extractEvolutionChain = (chain) => {
+  const evolutions = [chain.species.name];
+  let next = chain.evolves_to;
+  
+  while (next.length) {
+    evolutions.push(next[0].species.name);
+    next = next[0].evolves_to;
+  }
+  
+  return evolutions;
+};
+
+/**
+ * Gets the evolution chain of a given Pokémon by name or ID.
+ * @param {string|number} identifier
+ * @returns {Promise<void>}
+ */
+const getPokemonEvolutionChain = (identifier) =>
+  getEvolutionChainUrl(identifier)
+    .then(getEvolutionChain)
+    .then((evolutions) => console.log(`Evolution chain: ${evolutions.join(" → ")}`))
+    .catch((error) => console.error(`Failed to fetch evolution chain: ${error}`));
+
+// Test cases
+getPokemonEvolutionChain("pikachu"); // Pikachu's evolution chain
+getPokemonEvolutionChain(40);        // Pokémon with ID 40