cosine similarity

cosine.ts

function cosineSimilarity(a: number[], b: number[]): number {
  const dot = a.reduce((s, ai, i) => s + ai * (b[i] ?? 0), 0);
  const na = Math.sqrt(a.reduce((s, ai) => s + ai * ai, 0));
  const nb = Math.sqrt(b.reduce((s, bi) => s + bi * bi, 0));
  return dot / (na * nb);
}

type Vec = { id: string; vector: number[] };
const embeddings: Vec[] = [
  { id: "1", vector: [0.1, 0.2, 0.3] },
  { id: "2", vector: [0.2, 0.1, 0.4] },
  { id: "3", vector: [0.9, 0.8, 0.1] },
];

const query = [0.2, 0.2, 0.3];

const ranked = embeddings
  .map((e) => ({ ...e, score: cosineSimilarity(query, e.vector) }))
  .sort((a, b) => b.score - a.score);

console.log("ranked by cosine similarity:", ranked);