在JavaScript中深度克隆对象最有效的方法是什么?
克隆JavaScript对象最有效的方法是什么?我见过在JavaScript中深度克隆对象最有效的方法是什么?,javascript,object,clone,Javascript,Object,Clone,克隆JavaScript对象最有效的方法是什么?我见过obj=eval(uneval(o))正在使用,但是。我做过类似于obj=JSON.parse(JSON.stringify(o))但质疑效率我还看到了带有各种缺陷的递归复制函数。 我很惊讶没有标准解决方案存在。如果没有任何内置解决方案,您可以尝试: function clone(obj) { if (obj === null || typeof (obj) !== 'object' || 'isActiveClone' in ob
obj=eval(uneval(o))代码>正在使用,但是。
我做过类似于obj=JSON.parse(JSON.stringify(o))代码>但质疑效率
我还看到了带有各种缺陷的递归复制函数。
我很惊讶没有标准解决方案存在。如果没有任何内置解决方案,您可以尝试:
function clone(obj) {
if (obj === null || typeof (obj) !== 'object' || 'isActiveClone' in obj)
return obj;
if (obj instanceof Date)
var temp = new obj.constructor(); //or new Date(obj);
else
var temp = obj.constructor();
for (var key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
obj['isActiveClone'] = null;
temp[key] = clone(obj[key]);
delete obj['isActiveClone'];
}
}
return temp;
}
本地深度克隆
它被称为“结构化克隆”,在Node11和更高版本中进行实验,有望在浏览器中实现。有关更多详细信息,请参阅
数据丢失的快速克隆-JSON.parse/stringify
如果不在对象中使用日期、函数、未定义、无限、regexp、映射、集合、blob、文件列表、图像数据、稀疏数组、类型化数组或其他复杂类型,则深度克隆对象的非常简单的一行程序是:
JSON.parse(JSON.stringify(object))
const a={
字符串:“字符串”,
电话:123,
布尔:错,
nul:null,
日期:新日期(),//字符串化
未定义:未定义,//丢失
inf:Infinity,//强制为“null”
回复://.//,//丢失
}
控制台日志(a);
console.log(a.date的类型);//日期对象
const clone=JSON.parse(JSON.stringify(a));
console.log(克隆);
console.log(type of clone.date);//.toISOString()的结果
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:
这就是我正在使用的:
function cloneObject(obj) {
var clone = {};
for(var i in obj) {
if(typeof(obj[i])=="object" && obj[i] != null)
clone[i] = cloneObject(obj[i]);
else
clone[i] = obj[i];
}
return clone;
}
Crockford建议(我更喜欢)使用此函数:
function object(o) {
function F() {}
F.prototype = o;
return new F();
}
var newObject = object(oldObject);
它的简洁,工作如预期,你不需要一个图书馆
编辑:
var arr1 = [{object:'a'}, {object:'b'}];
这是对象的多边形填充。创建,因此您也可以使用它
var newObject = Object.create(oldObject);
注意:如果您使用其中一些,您可能会遇到使用hasOwnProperty
的某些迭代的问题。因为,create
创建继承oldObject
的新空对象。但它对于克隆对象仍然是有用和实用的
例如,如果oldObject.a=5代码>
newObject.a; // is 5
但是:
对于类似阵列的对象,似乎还没有理想的深度克隆操作符。正如下面的代码所示,John Resig的jQuery克隆器将具有非数字属性的数组转换为非数组的对象,而RegDwight的JSON克隆器则删除非数字属性。以下测试在多个浏览器上演示了这些要点:
function jQueryClone(obj) {
return jQuery.extend(true, {}, obj)
}
function JSONClone(obj) {
return JSON.parse(JSON.stringify(obj))
}
var arrayLikeObj = [[1, "a", "b"], [2, "b", "a"]];
arrayLikeObj.names = ["m", "n", "o"];
var JSONCopy = JSONClone(arrayLikeObj);
var jQueryCopy = jQueryClone(arrayLikeObj);
alert("Is arrayLikeObj an array instance?" + (arrayLikeObj instanceof Array) +
"\nIs the jQueryClone an array instance? " + (jQueryCopy instanceof Array) +
"\nWhat are the arrayLikeObj names? " + arrayLikeObj.names +
"\nAnd what are the JSONClone names? " + JSONCopy.names)
if (!Object.assign) {
Object.defineProperty(Object, 'assign', {
enumerable: false,
configurable: true,
writable: true,
value: function(target) {
'use strict';
if (target === undefined || target === null) {
throw new TypeError('Cannot convert first argument to object');
}
var to = Object(target);
for (var i = 1; i < arguments.length; i++) {
var nextSource = arguments[i];
if (nextSource === undefined || nextSource === null) {
continue;
}
nextSource = Object(nextSource);
var keysArray = Object.keys(nextSource);
for (var nextIndex = 0, len = keysArray.length; nextIndex < len; nextIndex++) {
var nextKey = keysArray[nextIndex];
var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey);
if (desc !== undefined && desc.enumerable) {
to[nextKey] = nextSource[nextKey];
}
}
}
return to;
}
});
}
假设对象中只有变量而没有函数,则可以使用:
var newObject = JSON.parse(JSON.stringify(oldObject));
检查此基准:
在我之前的测试中,我发现速度是一个主要问题
JSON.parse(JSON.stringify(obj))
是深度克隆对象的最慢方式(比deep
标志设置为true时慢10-20%)
当deep
标志设置为false
(浅克隆)时,jQuery.extend速度非常快。这是一个很好的选择,因为它包含一些额外的类型验证逻辑,不会复制未定义的属性等,但这也会使您的速度降低一点
如果您知道要克隆的对象的结构,或者可以避免深层嵌套数组,那么您可以编写一个简单的for(obj中的var i)
循环来克隆您的对象,同时检查hasOwnProperty,这将比jQuery快得多
最后,如果您试图在热循环中克隆一个已知的对象结构,只需将克隆过程排成一行并手动构建对象,就可以获得更高的性能
JavaScript跟踪引擎在优化for..in
循环和检查hasOwnProperty方面做得很差,也会降低速度。速度绝对必需时手动克隆
var clonedObject = {
knownProp: obj.knownProp,
..
}
注意在Date
objects-JSON.stringify(new Date())
上使用JSON.parse(JSON.stringify(obj))
方法返回ISO格式的日期字符串表示形式,而JSON.parse()
不会转换回Date
对象
此外,请注意,至少在Chrome 65中,本机克隆不是一条可行之路。根据JSPerf的说法,通过创建一个新函数来执行本机克隆几乎比使用JSON.stringify慢800x,而JSON.stringify在所有方面都非常快
如果您使用的是Javascript ES6,请尝试此本机方法进行克隆或浅拷贝
Object.assign({}, obj);
这通常不是最有效的解决方案,但它满足了我的需要。下面是简单的测试用例
function clone(obj, clones) {
// Makes a deep copy of 'obj'. Handles cyclic structures by
// tracking cloned obj's in the 'clones' parameter. Functions
// are included, but not cloned. Functions members are cloned.
var new_obj,
already_cloned,
t = typeof obj,
i = 0,
l,
pair;
clones = clones || [];
if (obj === null) {
return obj;
}
if (t === "object" || t === "function") {
// check to see if we've already cloned obj
for (i = 0, l = clones.length; i < l; i++) {
pair = clones[i];
if (pair[0] === obj) {
already_cloned = pair[1];
break;
}
}
if (already_cloned) {
return already_cloned;
} else {
if (t === "object") { // create new object
new_obj = new obj.constructor();
} else { // Just use functions as is
new_obj = obj;
}
clones.push([obj, new_obj]); // keep track of objects we've cloned
for (key in obj) { // clone object members
if (obj.hasOwnProperty(key)) {
new_obj[key] = clone(obj[key], clones);
}
}
}
}
return new_obj || obj;
}
功能测试
f = new Function
f.a = a
ff = clone(f)
ff === f //=> true
ff.a === a //=> false
我知道这是一个老帖子,但我想这可能会对下一个跌跌撞撞的人有所帮助
只要不将对象指定给任何对象,它就不会在内存中保持引用。因此,要创建一个要在其他对象之间共享的对象,必须创建如下工厂:
var a = function(){
return {
father:'zacharias'
};
},
b = a(),
c = a();
c.father = 'johndoe';
alert(b.father);
如果您正在使用它,库中有一个方法
结构化克隆
HTML标准包括可以创建对象深层克隆的。它仍然局限于某些内置类型,但除了JSON支持的少数类型之外,它还支持日期、regexp、映射、集合、blob、文件列表、ImageDatas、稀疏数组、类型化数组,将来可能还会支持更多。它还保留克隆数据中的引用,允许它支持可能导致JSON错误的循环和递归结构
Node.js中的支持:实验性浅拷贝一行():
和浅拷贝一行(,2015):
下面是一个全面的clone()方法,它可以克隆任何JavaScript对象。它处理几乎所有的情况:
function clone(src, deep) {
var toString = Object.prototype.toString;
if (!src && typeof src != "object") {
// Any non-object (Boolean, String, Number), null, undefined, NaN
return src;
}
// Honor native/custom clone methods
if (src.clone && toString.call(src.clone) == "[object Function]") {
return src.clone(deep);
}
// DOM elements
if (src.nodeType && toString.call(src.cloneNode) == "[object Function]") {
return src.cloneNode(deep);
}
// Date
if (toString.call(src) == "[object Date]") {
return new Date(src.getTime());
}
// RegExp
if (toString.call(src) == "[object RegExp]") {
return new RegExp(src);
}
// Function
if (toString.call(src) == "[object Function]") {
//Wrap in another method to make sure == is not true;
//Note: Huge performance issue due to closures, comment this :)
return (function(){
src.apply(this, arguments);
});
}
var ret, index;
//Array
if (toString.call(src) == "[object Array]") {
//[].slice(0) would soft clone
ret = src.slice();
if (deep) {
index = ret.length;
while (index--) {
ret[index] = clone(ret[index], true);
}
}
}
//Object
else {
ret = src.constructor ? new src.constructor() : {};
for (var prop in src) {
ret[prop] = deep
? clone(src[prop], true)
: src[prop];
}
}
return ret;
};
有一个,它做得很好。它提供了我所知的最完整的任意对象的递归克隆/复制。它还支持循环引用,这在其他答案中尚未涉及
你也可以。它可以用于浏览器和Node.js
下面是一个关于如何使用它的示例:
安装它与
npm install clone
或者把它包起来。
var a = function(){
return {
father:'zacharias'
};
},
b = a(),
c = a();
c.father = 'johndoe';
alert(b.father);
var newObject = _.clone(oldObject);
var origin = { foo : {} };
var copy = Object.keys(origin).reduce(function(c,k){c[k]=origin[k];return c;},{});
console.log(origin, copy);
console.log(origin == copy); // false
console.log(origin.foo == copy.foo); // true
var origin = { foo : {} };
var copy = Object.assign({}, origin);
console.log(origin, copy);
console.log(origin == copy); // false
console.log(origin.foo == copy.foo); // true
function clone(src, deep) {
var toString = Object.prototype.toString;
if (!src && typeof src != "object") {
// Any non-object (Boolean, String, Number), null, undefined, NaN
return src;
}
// Honor native/custom clone methods
if (src.clone && toString.call(src.clone) == "[object Function]") {
return src.clone(deep);
}
// DOM elements
if (src.nodeType && toString.call(src.cloneNode) == "[object Function]") {
return src.cloneNode(deep);
}
// Date
if (toString.call(src) == "[object Date]") {
return new Date(src.getTime());
}
// RegExp
if (toString.call(src) == "[object RegExp]") {
return new RegExp(src);
}
// Function
if (toString.call(src) == "[object Function]") {
//Wrap in another method to make sure == is not true;
//Note: Huge performance issue due to closures, comment this :)
return (function(){
src.apply(this, arguments);
});
}
var ret, index;
//Array
if (toString.call(src) == "[object Array]") {
//[].slice(0) would soft clone
ret = src.slice();
if (deep) {
index = ret.length;
while (index--) {
ret[index] = clone(ret[index], true);
}
}
}
//Object
else {
ret = src.constructor ? new src.constructor() : {};
for (var prop in src) {
ret[prop] = deep
? clone(src[prop], true)
: src[prop];
}
}
return ret;
};
npm install clone
ender build clone [...]
var clone = require('clone');
var a = { foo: { bar: 'baz' } }; // inital value of a
var b = clone(a); // clone a -> b
a.foo.bar = 'foo'; // change a
console.log(a); // { foo: { bar: 'foo' } }
console.log(b); // { foo: { bar: 'baz' } }
//If Object.create isn't already defined, we just do the simple shim,
//without the second argument, since that's all we need here
var object_create = Object.create;
if (typeof object_create !== 'function') {
object_create = function(o) {
function F() {}
F.prototype = o;
return new F();
};
}
function deepCopy(obj) {
if(obj == null || typeof(obj) !== 'object'){
return obj;
}
//make sure the returned object has the same prototype as the original
var ret = object_create(obj.constructor.prototype);
for(var key in obj){
ret[key] = deepCopy(obj[key]);
}
return ret;
}
/**
* Deep copy an object (make copies of all its object properties, sub-properties, etc.)
* An improved version of http://keithdevens.com/weblog/archive/2007/Jun/07/javascript.clone
* that doesn't break if the constructor has required parameters
*
* It also borrows some code from http://stackoverflow.com/a/11621004/560114
*/
function deepCopy(src, /* INTERNAL */ _visited, _copiesVisited) {
if(src === null || typeof(src) !== 'object'){
return src;
}
//Honor native/custom clone methods
if(typeof src.clone == 'function'){
return src.clone(true);
}
//Special cases:
//Date
if(src instanceof Date){
return new Date(src.getTime());
}
//RegExp
if(src instanceof RegExp){
return new RegExp(src);
}
//DOM Element
if(src.nodeType && typeof src.cloneNode == 'function'){
return src.cloneNode(true);
}
// Initialize the visited objects arrays if needed.
// This is used to detect cyclic references.
if (_visited === undefined){
_visited = [];
_copiesVisited = [];
}
// Check if this object has already been visited
var i, len = _visited.length;
for (i = 0; i < len; i++) {
// If so, get the copy we already made
if (src === _visited[i]) {
return _copiesVisited[i];
}
}
//Array
if (Object.prototype.toString.call(src) == '[object Array]') {
//[].slice() by itself would soft clone
var ret = src.slice();
//add it to the visited array
_visited.push(src);
_copiesVisited.push(ret);
var i = ret.length;
while (i--) {
ret[i] = deepCopy(ret[i], _visited, _copiesVisited);
}
return ret;
}
//If we've reached here, we have a regular object
//make sure the returned object has the same prototype as the original
var proto = (Object.getPrototypeOf ? Object.getPrototypeOf(src): src.__proto__);
if (!proto) {
proto = src.constructor.prototype; //this line would probably only be reached by very old browsers
}
var dest = object_create(proto);
//add this object to the visited array
_visited.push(src);
_copiesVisited.push(dest);
for (var key in src) {
//Note: this does NOT preserve ES5 property attributes like 'writable', 'enumerable', etc.
//For an example of how this could be modified to do so, see the singleMixin() function
dest[key] = deepCopy(src[key], _visited, _copiesVisited);
}
return dest;
}
//If Object.create isn't already defined, we just do the simple shim,
//without the second argument, since that's all we need here
var object_create = Object.create;
if (typeof object_create !== 'function') {
object_create = function(o) {
function F() {}
F.prototype = o;
return new F();
};
}
var clone = JSON.parse(JSON.stringify(obj));
var objects = [{ 'a': 1 }, { 'b': 2 }];
var deep = _.cloneDeep(objects);
console.log(deep[0] === objects[0]);
// => false
var arr1 = ['a', 'b', 'c'];
var arr2 = arr1;
arr1 = ['a', 'b', 'c'];
var arr1 = ['a', 'b', 'c']; // Becomes arr1 = ['a', 'b', 'c']
var arr2a = arr1.slice(0); // Becomes arr2a = ['a', 'b', 'c'] - deep copy
var arr2b = arr1.concat(); // Becomes arr2b = ['a', 'b', 'c'] - deep copy
var arr1 = [{object:'a'}, {object:'b'}];
function copy(o) {
var out, v, key;
out = Array.isArray(o) ? [] : {};
for (key in o) {
v = o[key];
out[key] = (typeof v === "object" && v !== null) ? copy(v) : v;
}
return out;
}
copy(arr1);
$.extend(true, [], arr1); // Jquery Extend
JSON.parse(arr1);
_.cloneDeep(arr1); // Lo-dash
var objToCreate = JSON.parse(JSON.stringify(cloneThis));
function clone(target, source){
for(let key in source){
// Use getOwnPropertyDescriptor instead of source[key] to prevent from trigering setter/getter.
let descriptor = Object.getOwnPropertyDescriptor(source, key);
if(descriptor.value instanceof String){
target[key] = new String(descriptor.value);
}
else if(descriptor.value instanceof Array){
target[key] = clone([], descriptor.value);
}
else if(descriptor.value instanceof Object){
let prototype = Reflect.getPrototypeOf(descriptor.value);
let cloneObject = clone({}, descriptor.value);
Reflect.setPrototypeOf(cloneObject, prototype);
target[key] = cloneObject;
}
else {
Object.defineProperty(target, key, descriptor);
}
}
let prototype = Reflect.getPrototypeOf(source);
Reflect.setPrototypeOf(target, prototype);
return target;
}
var clone = Object.assign({}, obj);
if (!Object.assign) {
Object.defineProperty(Object, 'assign', {
enumerable: false,
configurable: true,
writable: true,
value: function(target) {
'use strict';
if (target === undefined || target === null) {
throw new TypeError('Cannot convert first argument to object');
}
var to = Object(target);
for (var i = 1; i < arguments.length; i++) {
var nextSource = arguments[i];
if (nextSource === undefined || nextSource === null) {
continue;
}
nextSource = Object(nextSource);
var keysArray = Object.keys(nextSource);
for (var nextIndex = 0, len = keysArray.length; nextIndex < len; nextIndex++) {
var nextKey = keysArray[nextIndex];
var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey);
if (desc !== undefined && desc.enumerable) {
to[nextKey] = nextSource[nextKey];
}
}
}
return to;
}
});
}
var newObject = angular.copy(oldObject);
var obj = {a:1, b:2, c:3, d:4};
function deepCopyObj(obj) {
if (null == obj || "object" != typeof obj) return obj;
if (obj instanceof Date) {
var copy = new Date();
copy.setTime(obj.getTime());
return copy;
}
if (obj instanceof Array) {
var copy = [];
for (var i = 0, len = obj.length; i < len; i++) {
copy[i] = deepCopyObj(obj[i]);
}
return copy;
}
if (obj instanceof Object) {
var copy = {};
for (var attr in obj) {
if (obj.hasOwnProperty(attr)) copy[attr] = deepCopyObj(obj[attr]);
}
return copy;
}
throw new Error("Unable to copy obj this object.");
}
var deepCopyObj = JSON.parse(JSON.stringify(obj));
var deepCopyObj = angular.copy(obj);
var deepCopyObj = jQuery.extend(true, {}, obj);
var deepCopyObj = _.cloneDeep(obj); //latest version UndescoreJs makes shallow copy
function cloneObject(obj) {
if (obj === null || typeof(obj) !== 'object')
return obj;
var temp = obj.constructor(); // changed
for (var key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
obj['isActiveClone'] = null;
temp[key] = cloneObject(obj[key]);
delete obj['isActiveClone'];
}
}
return temp;
}
var b = cloneObject({"a":1,"b":2}); // calling
var a = {"a":1,"b":2};
var b = JSON.parse(JSON.stringify(a));
var a = {"a":1,"b":2};
// Deep copy
var newObject = jQuery.extend(true, {}, a);
var obj = {
a: 1,
b: {
c: 2
}
}
var newObj = JSON.parse(JSON.stringify(obj));
obj.b.c = 20;
console.log(obj); // { a: 1, b: { c: 20 } }
console.log(newObj); // { a: 1, b: { c: 2 } }
function cloneObject(obj) {
var clone = {};
for(var i in obj) {
if(obj[i] != null && typeof(obj[i])=="object")
clone[i] = cloneObject(obj[i]);
else
clone[i] = obj[i];
}
return clone;
}
var obj = {
a: 1,
b: {
c: 2
}
}
var newObj = cloneObject(obj);
obj.b.c = 20;
console.log(obj); // { a: 1, b: { c: 20 } }
console.log(newObj); // { a: 1, b: { c: 2 } }
var obj = {
a: 1,
b: {
c: 2
}
}
var newObj = _.cloneDeep(obj);
obj.b.c = 20;
console.log(obj); // { a: 1, b: { c: 20 } }
console.log(newObj); // { a: 1, b: { c: 2 } }
var obj = {
a: 1,
b: 2
}
var newObj = _.clone(obj);
obj.b = 20;
console.log(obj); // { a: 1, b: 20 }
console.log(newObj); // { a: 1, b: 2 }
var obj = {
a: 1,
b: {
c: 2
}
}
var newObj = Object.assign({}, obj);
obj.b.c = 20;
console.log(obj); // { a: 1, b: { c: 20 } }
console.log(newObj); // { a: 1, b: { c: 20 } } --> WRONG
// Note: Properties on the prototype chain and non-enumerable properties cannot be copied.
var obj = {
a: 1,
b: 2
}
var newObj = _.clone(obj);
obj.b = 20;
console.log(obj); // { a: 1, b: 20 }
console.log(newObj); // { a: 1, b: 2 }
var obj = {
a: 1,
b: {
c: 2
}
}
var newObj = _.cloneDeep(obj);
obj.b.c = 20;
console.log(obj); // { a: 1, b: { c: 20 } }
console.log(newObj); // { a: 1, b: { c: 20 } } --> WRONG
// (Create a shallow-copied clone of the provided plain object. Any nested objects or arrays will be copied by reference, not duplicated.)