什么是最有效的方式来克隆一个JavaScript对象?我已经看到obj = eval(uneval(o));被使用,但它是非标准的,仅支持Firefox.我做了事情,如obj = JSON.parse(JSON.stringify(o));但质疑效率。
当前回答
下面是我如何深度克隆一个与ES2015默认值和扩展操作器的对象
const makeDeepCopy = (obj, copy = {}) => {
for (let item in obj) {
if (typeof obj[item] === 'object') {
makeDeepCopy(obj[item], copy)
}
if (obj.hasOwnProperty(item)) {
copy = {
...obj
}
}
}
return copy
}
const testObj = {“类型”:“对象”,“属性”: {“用户Id”: {“类型”:“string”,“机会”:“指南” },“emailAddr”: {“类型”:“string”,“机会”: {“电子邮件”: {“域名”:“fake.com” },“模式”:“+@fake.com” },“需要”: {“用户Id”,“emailAddr” } } const makeDeepCopy = (ob)
其他回答
只是因为我没有看到AngularJS提到并认为人们可能想知道......
angular.copy 还提供深复制对象和序列的方法。
克罗克福德建议(我更喜欢)使用此功能:
function object(o) {
function F() {}
F.prototype = o;
return new F();
}
var newObject = object(oldObject);
它是干净的,工作如预期,你不需要图书馆。
编辑:
这是一个对 Object.create 的聚合物,所以你也可以使用它。
var newObject = Object.create(oldObject);
注意: 如果你使用其中的一些,你可能有问题与某些 iteration谁使用 hasOwnProperty. 因为,创建创造新的空的对象,继承旧的对象. 但它仍然有用和实用的克隆对象。
例如,如果 oldObject.a = 5;
newObject.a; // is 5
但:
oldObject.hasOwnProperty(a); // is true
newObject.hasOwnProperty(a); // is false
代码:
// extends 'from' object with members from 'to'. If 'to' is null, a deep clone of 'from' is returned
function extend(from, to)
{
if (from == null || typeof from != "object") return from;
if (from.constructor != Object && from.constructor != Array) return from;
if (from.constructor == Date || from.constructor == RegExp || from.constructor == Function ||
from.constructor == String || from.constructor == Number || from.constructor == Boolean)
return new from.constructor(from);
to = to || new from.constructor();
for (var name in from)
{
to[name] = typeof to[name] == "undefined" ? extend(from[name], null) : to[name];
}
return to;
}
测试:
var obj =
{
date: new Date(),
func: function(q) { return 1 + q; },
num: 123,
text: "asdasd",
array: [1, "asd"],
regex: new RegExp(/aaa/i),
subobj:
{
num: 234,
text: "asdsaD"
}
}
var clone = extend(obj);
// obj target object, vals source object
var setVals = function (obj, vals) {
if (obj && vals) {
for (var x in vals) {
if (vals.hasOwnProperty(x)) {
if (obj[x] && typeof vals[x] === 'object') {
obj[x] = setVals(obj[x], vals[x]);
} else {
obj[x] = vals[x];
}
}
}
}
return obj;
};
结构化克隆
HTML 标准包含一个内部结构化的克隆/序列化算法,可以创建对象的深度克隆,它仍然仅限于某些内置类型,但除了由 JSON 支持的少数类型之外,它还支持日期、RegExps、地图、套件、Blobs、FileLists、ImageDatas、Sparse Arrays、Typed Arrays等。
结构化Clone 全球功能由 Node 17.0 提供:
const clone = structuredClone(original);
以前版本: Node.js 的 v8 模块(如 Node 11 )直接展示了结构化序列化 API,但此功能仍然被标记为“实验性”,并在未来的版本中可更改或删除。
const v8 = require('v8');
const structuredClone = obj => {
return v8.deserialize(v8.serialize(obj));
};
直接支持浏览器:可用于Firefox 94
const clone = structuredClone(original);
class StructuredCloner {
constructor() {
this.pendingClones_ = new Map();
this.nextKey_ = 0;
const channel = new MessageChannel();
this.inPort_ = channel.port1;
this.outPort_ = channel.port2;
this.outPort_.onmessage = ({data: {key, value}}) => {
const resolve = this.pendingClones_.get(key);
resolve(value);
this.pendingClones_.delete(key);
};
this.outPort_.start();
}
cloneAsync(value) {
return new Promise(resolve => {
const key = this.nextKey_++;
this.pendingClones_.set(key, resolve);
this.inPort_.postMessage({key, value});
});
}
}
const structuredCloneAsync = window.structuredCloneAsync =
StructuredCloner.prototype.cloneAsync.bind(new StructuredCloner);
const main = async () => {
const original = { date: new Date(), number: Math.random() };
original.self = original;
const clone = await structuredCloneAsync(original);
// They're different objects:
console.assert(original !== clone);
console.assert(original.date !== clone.date);
// They're cyclical:
console.assert(original.self === original);
console.assert(clone.self === clone);
// They contain equivalent values:
console.assert(original.number === clone.number);
console.assert(Number(original.date) === Number(clone.date));
console.log("Assertions complete.");
};
main();
const structuredClone = obj => {
const oldState = history.state;
history.replaceState(obj, null);
const clonedObj = history.state;
history.replaceState(oldState, null);
return clonedObj;
};
雖然同步,但這可能非常慢。 它發生了所有與操縱瀏覽器歷史相關的頭部. 重複召喚這種方法可能會導致Chrome暫時變成無責任。
const structuredClone = obj => {
const n = new Notification('', {data: obj, silent: true});
n.onshow = n.close.bind(n);
return n.data;
};