ReadOnlyMap

index.js

const _ = Symbol('private');

class ReadOnlyMap {
  constructor(map) {
    this[_] = map;
  }

  static from(entries) {
    return new ReadOnlyMap(new Map(entries));
  }

  get size() {
    return this[_].size;
  }

  has(type) {
    return this[_].has(type);
  }

  get(type) {
    return this[_].get(type);
  }

  set() {
    throw new Error('readOnlyMap.set is unimplemented');
  }

  delete() {
    throw new Error('readOnlyMap.delete is unimplemented');
  }

  clear() {
    throw new Error('readOnlyMap.clear is unimplemented');
  }

  keys() {
    return this[_].keys();
  }

  values() {
    return this[_].values();
  }

  entries() {
    return this[_].entries();
  }

  forEach(fn) {
    return this[_].forEach(fn);
  }

  [Symbol.iterator]() {
    return this[_][Symbol.iterator]();
  }
}