我有一个对象x。我想将其复制为对象y,这样对y的更改不会修改x。我意识到复制从内置JavaScript对象派生的对象会导致额外的、不需要的财产。这不是问题,因为我正在复制我自己的一个文字构造对象。
如何正确克隆JavaScript对象?
我有一个对象x。我想将其复制为对象y,这样对y的更改不会修改x。我意识到复制从内置JavaScript对象派生的对象会导致额外的、不需要的财产。这不是问题,因为我正在复制我自己的一个文字构造对象。
如何正确克隆JavaScript对象?
当前回答
这是对A.Levy代码的修改,以处理函数和多个/循环引用的克隆。这意味着,如果克隆的树中的两个财产是同一对象的引用,则克隆的对象树将使这些财产指向被引用对象的同一克隆。这也解决了循环依赖性的问题,如果不加以处理,就会导致无限循环。算法的复杂度为O(n)
function clone(obj){
var clonedObjectsArray = [];
var originalObjectsArray = []; //used to remove the unique ids when finished
var next_objid = 0;
function objectId(obj) {
if (obj == null) return null;
if (obj.__obj_id == undefined){
obj.__obj_id = next_objid++;
originalObjectsArray[obj.__obj_id] = obj;
}
return obj.__obj_id;
}
function cloneRecursive(obj) {
if (null == obj || typeof obj == "string" || typeof obj == "number" || typeof obj == "boolean") return obj;
// Handle Date
if (obj instanceof Date) {
var copy = new Date();
copy.setTime(obj.getTime());
return copy;
}
// Handle Array
if (obj instanceof Array) {
var copy = [];
for (var i = 0; i < obj.length; ++i) {
copy[i] = cloneRecursive(obj[i]);
}
return copy;
}
// Handle Object
if (obj instanceof Object) {
if (clonedObjectsArray[objectId(obj)] != undefined)
return clonedObjectsArray[objectId(obj)];
var copy;
if (obj instanceof Function)//Handle Function
copy = function(){return obj.apply(this, arguments);};
else
copy = {};
clonedObjectsArray[objectId(obj)] = copy;
for (var attr in obj)
if (attr != "__obj_id" && obj.hasOwnProperty(attr))
copy[attr] = cloneRecursive(obj[attr]);
return copy;
}
throw new Error("Unable to copy obj! Its type isn't supported.");
}
var cloneObj = cloneRecursive(obj);
//remove the unique ids
for (var i = 0; i < originalObjectsArray.length; i++)
{
delete originalObjectsArray[i].__obj_id;
};
return cloneObj;
}
一些快速测试
var auxobj = {
prop1 : "prop1 aux val",
prop2 : ["prop2 item1", "prop2 item2"]
};
var obj = new Object();
obj.prop1 = "prop1_value";
obj.prop2 = [auxobj, auxobj, "some extra val", undefined];
obj.nr = 3465;
obj.bool = true;
obj.f1 = function (){
this.prop1 = "prop1 val changed by f1";
};
objclone = clone(obj);
//some tests i've made
console.log("test number, boolean and string cloning: " + (objclone.prop1 == obj.prop1 && objclone.nr == obj.nr && objclone.bool == obj.bool));
objclone.f1();
console.log("test function cloning 1: " + (objclone.prop1 == 'prop1 val changed by f1'));
objclone.f1.prop = 'some prop';
console.log("test function cloning 2: " + (obj.f1.prop == undefined));
objclone.prop2[0].prop1 = "prop1 aux val NEW";
console.log("test multiple references cloning 1: " + (objclone.prop2[1].prop1 == objclone.prop2[0].prop1));
console.log("test multiple references cloning 2: " + (objclone.prop2[1].prop1 != obj.prop2[0].prop1));
其他回答
根据MDN:
如果要浅层复制,请使用Object.assign({},a)对于“深度”复制,请使用JSON.parse(JSON.stringify(a))
不需要外部库,但您需要首先检查浏览器兼容性。
如果您的对象是类(例如。https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes):
var copiedObject = jQuery.extend(true, {}, originalObject);
copiedObject.__proto__ = originalObject.__proto__;
然后在copiedObject中,您有一个originalObject类及其所有方法的深度复制实例。
这是对A.Levy代码的修改,以处理函数和多个/循环引用的克隆。这意味着,如果克隆的树中的两个财产是同一对象的引用,则克隆的对象树将使这些财产指向被引用对象的同一克隆。这也解决了循环依赖性的问题,如果不加以处理,就会导致无限循环。算法的复杂度为O(n)
function clone(obj){
var clonedObjectsArray = [];
var originalObjectsArray = []; //used to remove the unique ids when finished
var next_objid = 0;
function objectId(obj) {
if (obj == null) return null;
if (obj.__obj_id == undefined){
obj.__obj_id = next_objid++;
originalObjectsArray[obj.__obj_id] = obj;
}
return obj.__obj_id;
}
function cloneRecursive(obj) {
if (null == obj || typeof obj == "string" || typeof obj == "number" || typeof obj == "boolean") return obj;
// Handle Date
if (obj instanceof Date) {
var copy = new Date();
copy.setTime(obj.getTime());
return copy;
}
// Handle Array
if (obj instanceof Array) {
var copy = [];
for (var i = 0; i < obj.length; ++i) {
copy[i] = cloneRecursive(obj[i]);
}
return copy;
}
// Handle Object
if (obj instanceof Object) {
if (clonedObjectsArray[objectId(obj)] != undefined)
return clonedObjectsArray[objectId(obj)];
var copy;
if (obj instanceof Function)//Handle Function
copy = function(){return obj.apply(this, arguments);};
else
copy = {};
clonedObjectsArray[objectId(obj)] = copy;
for (var attr in obj)
if (attr != "__obj_id" && obj.hasOwnProperty(attr))
copy[attr] = cloneRecursive(obj[attr]);
return copy;
}
throw new Error("Unable to copy obj! Its type isn't supported.");
}
var cloneObj = cloneRecursive(obj);
//remove the unique ids
for (var i = 0; i < originalObjectsArray.length; i++)
{
delete originalObjectsArray[i].__obj_id;
};
return cloneObj;
}
一些快速测试
var auxobj = {
prop1 : "prop1 aux val",
prop2 : ["prop2 item1", "prop2 item2"]
};
var obj = new Object();
obj.prop1 = "prop1_value";
obj.prop2 = [auxobj, auxobj, "some extra val", undefined];
obj.nr = 3465;
obj.bool = true;
obj.f1 = function (){
this.prop1 = "prop1 val changed by f1";
};
objclone = clone(obj);
//some tests i've made
console.log("test number, boolean and string cloning: " + (objclone.prop1 == obj.prop1 && objclone.nr == obj.nr && objclone.bool == obj.bool));
objclone.f1();
console.log("test function cloning 1: " + (objclone.prop1 == 'prop1 val changed by f1'));
objclone.f1.prop = 'some prop';
console.log("test function cloning 2: " + (obj.f1.prop == undefined));
objclone.prop2[0].prop1 = "prop1 aux val NEW";
console.log("test multiple references cloning 1: " + (objclone.prop2[1].prop1 == objclone.prop2[0].prop1));
console.log("test multiple references cloning 2: " + (objclone.prop2[1].prop1 != obj.prop2[0].prop1));
克隆对象的简单递归方法。也可以使用lodash.clone。
让克隆=(obj)=>{let obj2=Array.isArray(obj)?[] : {};for(设k为obj){obj2[k]=(obj[k]===“对象”的类型)?克隆(obj[k]):obj[k];}返回obj2;}让w={name:“Apple”,类型:[“Fuji”,“Gala”]};设x=克隆(w);w.name=“橙色”;w.types=[“Navel”];console.log(x);console.log(w);
本文来自Brian Huisman的《如何在Javascript中复制数组和对象》:
Object.prototype.clone = function() {
var newObj = (this instanceof Array) ? [] : {};
for (var i in this) {
if (i == 'clone') continue;
if (this[i] && typeof this[i] == "object") {
newObj[i] = this[i].clone();
} else newObj[i] = this[i]
} return newObj;
};