const root = { kids: new Map(), end: false };
function add(w) { let n = root; for (const c of w) { if (!n.kids.has(c)) n.kids.set(c, { kids: new Map(), end: false }); n = n.kids.get(c); } }
add("cat");
let n = root; let ok = true;
for (const c of "cat") { if (!n.kids.has(c)) { ok = false; break; } n = n.kids.get(c); }
document.querySelector('#out').textContent = ok && n.end ? "present" : "missing";