lib0/map.js

> Monorepo of isomorphic utility functions

/**
 * Utility module to work with key-value stores.
 *
 * @module map
 */

/**
 * Creates a new Map instance.
 *
 * @function
 * @return {Map<any, any>}
 *
 * @function
 */
export const create = () => new Map()

/**
 * Copy a Map object into a fresh Map object.
 *
 * @function
 * @template X,Y
 * @param {Map<X,Y>} m
 * @return {Map<X,Y>}
 */
export const copy = m => {
  const r = create()
  m.forEach((v, k) => { r.set(k, v) })
  return r
}

/**
 * Get map property. Create T if property is undefined and set T on map.
 *
 * ```js
 * const listeners = map.setIfUndefined(events, 'eventName', set.create)
 * listeners.add(listener)
 * ```
 *
 * @function
 * @template V,K
 * @template {Map<K,V>} MAP
 * @param {MAP} map
 * @param {K} key
 * @param {function():V} createT
 * @return {V}
 */
export const setIfUndefined = (map, key, createT) => {
  let set = map.get(key)
  if (set === undefined) {
    map.set(key, set = createT())
  }
  return set
}

/**
 * Creates an Array and populates it with the content of all key-value pairs using the `f(value, key)` function.
 *
 * @function
 * @template K
 * @template V
 * @template R
 * @param {Map<K,V>} m
 * @param {function(V,K):R} f
 * @return {Array<R>}
 */
export const map = (m, f) => {
  const res = []
  for (const [key, value] of m) {
    res.push(f(value, key))
  }
  return res
}

/**
 * Tests whether any key-value pairs pass the test implemented by `f(value, key)`.
 *
 * @todo should rename to some - similarly to Array.some
 *
 * @function
 * @template K
 * @template V
 * @param {Map<K,V>} m
 * @param {function(V,K):boolean} f
 * @return {boolean}
 */
export const any = (m, f) => {
  for (const [key, value] of m) {
    if (f(value, key)) {
      return true
    }
  }
  return false
}

/**
 * Tests whether all key-value pairs pass the test implemented by `f(value, key)`.
 *
 * @function
 * @template K
 * @template V
 * @param {Map<K,V>} m
 * @param {function(V,K):boolean} f
 * @return {boolean}
 */
export const all = (m, f) => {
  for (const [key, value] of m) {
    if (!f(value, key)) {
      return false
    }
  }
  return true
}