Is this better?
hero.findOpponent = function () {
for (let enemy of hero.findEnemies()) if (enemy.id.includes("Hero Placeholder")) return enemy;
return undefined;
};
hero.findData = function (u) {
let types = {assassin: "Ritic", intellectual: "Armando/Ned", knight: "Tharin", librarian: "Hushbaum", trapper: "Senick", sorcerer: "Pender", goliath: "Okar", duelist: "Alejandro", champion: "Ida", necromancer: "Nalfar", captain: "Anya", samurai: "Hattori", guardian: "Illia", pixie: "Zana"};
let uData = {hero: types[u.type], type: null};
if (!(uData.hero)) {
switch (u.type) {
case "forest-archer": return {hero: "Naria", type: "Ranger"};
case "potion-master": return {hero: "Omarn", type: "Wizard"};
case "master-wizard": return {hero: "Usara", type: "Wizard"};
}
}
u = uData.hero;
if (u === "Illia" || u === "Anya" || u === "Tharin" || u === "Okar" || u === "Alejandro" || u === "Ida" || u === "Hattori" || u === "Arryn" || u === "Gordon" || u === "Armando/Ned") uData.type = "Warrior";
if (u === "Zana" || u === "Senick" || u === "Ritic" || u === "Amara") uData.type = "Ranger";
if (u === "Hushbaum" || u === "Nalfar" || u === "Pender") uData.type = "Wizard";
return uData;
};
Sorry about the delay 
I had to go to school…