let clonedMap = new Map(originalMap);
let clonedSet = new Set(originalSet);
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])))
let originalMap = new Map()
let data = {a:'a',b:'b'}
originalMap.set(1,data)
let shallowCloned = new Map(originalMap)
let deepCloned = new Map(JSON.parse(JSON.stringify([...originalMap])))
data.a = 'p'
console.log('originalMap:',[...originalMap])
console.log('shallowCloned:',[...shallowCloned])
console.log('deepCloned:',[...deepCloned])
originalMap
里面还有其他的map/set,我猜这个方法就不会起作用了。 - Dmitry Koroliov使用 for 循环创建新 Set 对象比使用 Set 构造函数更快。对于 Map 对象也是一样(虽然程度较小)。
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))
new Set(set)
比setFromForLoop(set)
快大约15-20毫秒,但在Chrome中,setFromForLoop(set)
比new Set(set)
快大约20-28毫秒。 - MagnecloneSet()
函数,并在文档中说明为什么要使用它而不是 Set
构造函数,或者简单地提供一个链接到这个答案。 - Amit Beckensteinconst mySet = new Set([1, 2, 3, 4]);
const myCloneSet = new Set(Array.from(mySet));
console.log(mySet === myCloneSet) //false
我需要复制(“克隆”)一个JavaScript集,而这个问题引起了我的兴趣,关于那个克隆副本的完整性,对于那些副本的源发生扰动。
测试
var fruit = new Set(['apples', 'bananas']);
var provinces = new Set(['british columbia', 'nova scotia']);
console.log('fruit:', fruit)
console.log('provinces:', provinces)
// fruit: Set [ "apples", "bananas" ]
// provinces: Set [ "british columbia", "nova scotia" ]
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set#implementing_basic_set_operations
function unionSets(setA, setB) {
let _union = new Set(setA);
for (let elem of setB) {
_union.add(elem)
}
return _union;
}
myUnionSet = unionSets(fruit, provinces);
console.log('myUnionSet:', myUnionSet)
// myUnionSet: Set(4) [ "apples", "bananas", "british columbia", "nova scotia" ]
// Tests:
fruit.delete('apples');
provinces.delete('british columbia');
console.log('fruit:', fruit)
console.log('provinces:', provinces)
console.log('myUnionSet:', myUnionSet)
// fruit: Set [ "bananas" ]
// provinces: Set [ "nova scotia" ]
// myUnionSet: Set(4) [ "apples", "bananas", "british columbia", "nova scotia" ]
const newMap = new Map();
old.forEach((val, key) => newMap.set(key, [...old.get(key)]));
Map
应该被视为抽象数据类型,而不是 JavaScript 对象。因此深度克隆一个Map
没有意义。 - user6445533