在node.js中克隆对象的最佳方法是什么
例:我想避免以下情况:
var obj1 = {x: 5, y:5};
var obj2 = obj1;
obj2.x = 6;
console.log(obj1.x); // logs 6
对象很可能包含复杂类型作为属性,所以简单的for(var x in obj1)解决不了问题。我需要自己写一个递归克隆吗?还是有一些我没有看到的内置的东西?
在node.js中克隆对象的最佳方法是什么
例:我想避免以下情况:
var obj1 = {x: 5, y:5};
var obj2 = obj1;
obj2.x = 6;
console.log(obj1.x); // logs 6
对象很可能包含复杂类型作为属性,所以简单的for(var x in obj1)解决不了问题。我需要自己写一个递归克隆吗?还是有一些我没有看到的内置的东西?
当前回答
There is no built-in way to do a real clone (deep copy) of an object in node.js. There are some tricky edge cases so you should definitely use a library for this. I wrote such a function for my simpleoo library. You can use the deepCopy function without using anything else from the library (which is quite small) if you don't need it. This function supports cloning multiple data types, including arrays, dates, and regular expressions, it supports recursive references, and it also works with objects whose constructor functions have required parameters.
代码如下:
//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();
};
}
/**
* 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 = function deepCopy(src, /* INTERNAL */ _visited) {
if(src == null || typeof(src) !== 'object'){
return src;
}
// Initialize the visited objects array if needed
// This is used to detect cyclic references
if (_visited == undefined){
_visited = [];
}
// Ensure src has not already been visited
else {
var i, len = _visited.length;
for (i = 0; i < len; i++) {
// If src was already visited, don't try to copy it, just return the reference
if (src === _visited[i]) {
return src;
}
}
}
// Add this object to the visited array
_visited.push(src);
//Honor native/custom clone methods
if(typeof src.clone == 'function'){
return src.clone(true);
}
//Special cases:
//Array
if (Object.prototype.toString.call(src) == '[object Array]') {
//[].slice(0) would soft clone
ret = src.slice();
var i = ret.length;
while (i--){
ret[i] = deepCopy(ret[i], _visited);
}
return ret;
}
//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);
}
//If we've reached here, we have a regular object, array, or function
//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 ret = object_create(proto);
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
ret[key] = deepCopy(src[key], _visited);
}
return ret;
};
其他回答
如果你正在使用普通对象和数组,并且不关心克隆函数或递归引用,这里有一个简单的deepClone实现,它适用于普通对象、数组、字符串、数字、正则表达式、日期等。
// Simple Deep Clone
// Does not clone functions or handle recursive references.
function deepClone(original) {
if (original instanceof RegExp) {
return new RegExp(original);
} else if (original instanceof Date) {
return new Date(original.getTime());
} else if (Array.isArray(original)) {
return original.map(deepClone);
} else if (typeof original === 'object' && original !== null) {
const clone = {};
Object.keys(original).forEach(k => {
clone[k] = deepClone(original[k]);
});
return clone;
}
return original;
}
// Usage:
const obj = { n: 1, a: [ { a: 1 }, { a: 2 } ], d: new Date(), s: 'foo' };
const clone = deepClone(obj);
查看underscore.js。它具有克隆和扩展以及许多其他非常有用的功能。
这可能很有用:在Node.js中使用下划线模块
There is no built-in way to do a real clone (deep copy) of an object in node.js. There are some tricky edge cases so you should definitely use a library for this. I wrote such a function for my simpleoo library. You can use the deepCopy function without using anything else from the library (which is quite small) if you don't need it. This function supports cloning multiple data types, including arrays, dates, and regular expressions, it supports recursive references, and it also works with objects whose constructor functions have required parameters.
代码如下:
//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();
};
}
/**
* 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 = function deepCopy(src, /* INTERNAL */ _visited) {
if(src == null || typeof(src) !== 'object'){
return src;
}
// Initialize the visited objects array if needed
// This is used to detect cyclic references
if (_visited == undefined){
_visited = [];
}
// Ensure src has not already been visited
else {
var i, len = _visited.length;
for (i = 0; i < len; i++) {
// If src was already visited, don't try to copy it, just return the reference
if (src === _visited[i]) {
return src;
}
}
}
// Add this object to the visited array
_visited.push(src);
//Honor native/custom clone methods
if(typeof src.clone == 'function'){
return src.clone(true);
}
//Special cases:
//Array
if (Object.prototype.toString.call(src) == '[object Array]') {
//[].slice(0) would soft clone
ret = src.slice();
var i = ret.length;
while (i--){
ret[i] = deepCopy(ret[i], _visited);
}
return ret;
}
//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);
}
//If we've reached here, we have a regular object, array, or function
//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 ret = object_create(proto);
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
ret[key] = deepCopy(src[key], _visited);
}
return ret;
};
如果你不想“滚出你自己的”,还有一些Node模块。这个看起来不错:https://www.npmjs.com/package/clone
看起来它可以处理各种各样的东西,包括循环引用。来自github页面:
clone主人克隆对象,数组,日期对象和RegEx 对象。所有内容都是递归克隆的,因此您可以克隆日期 例如,在对象的数组中。[…循环推荐?是的!
没有一个答案让我满意,一些不工作或只是肤浅的克隆,答案来自@clint-harris和使用JSON。Parse /stringify很好,但是很慢。我找到了一个可以快速进行深度克隆的模块:https://github.com/AlexeyKupershtokh/node-v8-clone