meta.js

const metaMap = new WeakMap();
const getPrototypeOf = Object.getPrototypeOf;

function peekMeta(obj) {
  let o = obj;
  let m;
  while (o) {
    m = metaMap.get(o);
    if (m) return m;
    o = getPrototypeOf(o);
  }
}

function deleteMeta(obj) {
  metaMap.set(obj, null);
}

function setMeta(obj, meta) {
  metaMap.set(obj, meta);
}