浅克隆ES6地图或集

Question

你如何浅层克隆ES6 Map或Set对象？

我想获得一个具有相同键和值的新Map或Set.

Answer 1

使用构造函数克隆地图和集:

var clonedMap = new Map(originalMap)

var clonedSet = new Set(originalSet)

Answer 2

通过 for 循环创建新 Set 比 Set 构造函数更快。地图也是如此，尽管程度较轻。

const timeInLoop = (desc, loopCount, fn) => {
  const d = `${desc}: ${loopCount.toExponential()}`
  console.time(d)
  for (let i = 0; i < loopCount; i++) {
    fn()
  }
  console.timeEnd(d)
}

const set = new Set([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])

const setFromForLoop = x => {
  const y = new Set()
  for (const item of x) y.add(item)
  return y
}

const map = new Map([['a', 1], ['b', 2], ['c', 3], ['d', 4], ['e', 5]])

const mapFromForLoop = x => {
  const y = new Map()
  for (const entry of x) y.set(...entry)
  return y
}

timeInLoop('new Set(set)', 1e5, () => new Set(set))

timeInLoop('setFromForLoop(set)', 1e5, () => setFromForLoop(set))

timeInLoop('new Map(map)', 1e5, () => new Map(map))

timeInLoop('mapFromForLoop(map)', 1e5, () => mapFromForLoop(map))

Answer 3

浅克隆：

var clonedMap = new Map(originalMap)

var clonedSet = new Set(originalSet)

深度克隆：

var deepClonedMap = new Map(JSON.parse(JSON.stringify([...originalMap])))
var deepClonedSet = new Set(JSON.parse(JSON.stringify([...originalSet])))

var clonedMap = new Map(originalMap)

var clonedSet = new Set(originalSet)