mingo/dist/esm/operators/pipeline/lookup.js

MongoDB query language for in-memory objects

import { assert, hashCode, into, isString, resolve } from "../../util";
const $lookup = (collection, expr, options) => {
  const joinColl = isString(expr.from) ? options?.collectionResolver(expr.from) : expr.from;
  assert(joinColl instanceof Array, `'from' field must resolve to an array`);
  const hash = {};
  for (const obj of joinColl) {
    const k = hashCode(resolve(obj, expr.foreignField), options?.hashFunction);
    hash[k] = hash[k] || [];
    hash[k].push(obj);
  }
  return collection.map((obj) => {
    const k = hashCode(resolve(obj, expr.localField), options?.hashFunction);
    const newObj = into({}, obj);
    newObj[expr.as] = hash[k] || [];
    return newObj;
  });
};
export {
  $lookup
};