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
如果沒有任何內建一個,你可以嘗試:
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;
}
其他回答
这里是一个全面的克隆()方法,可以克隆任何JavaScript对象,它处理几乎所有情况:
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;
};
因为回归只是太昂贵的JavaScript,我发现的大多数答案是使用回归,而JSON方法将错过非JSON转换部分(功能等)。所以我做了一些研究,并发现这个拖拉机技术避免它。
/*
* Trampoline to avoid recursion in JavaScript, see:
* https://www.integralist.co.uk/posts/functional-recursive-javascript-programming/
*/
function trampoline() {
var func = arguments[0];
var args = [];
for (var i = 1; i < arguments.length; i++) {
args[i - 1] = arguments[i];
}
var currentBatch = func.apply(this, args);
var nextBatch = [];
while (currentBatch && currentBatch.length > 0) {
currentBatch.forEach(function(eachFunc) {
var ret = eachFunc();
if (ret && ret.length > 0) {
nextBatch = nextBatch.concat(ret);
}
});
currentBatch = nextBatch;
nextBatch = [];
}
};
/*
* Deep clone an object using the trampoline technique.
*
* @param target {Object} Object to clone
* @return {Object} Cloned object.
*/
function clone(target) {
if (typeof target !== 'object') {
return target;
}
if (target == null || Object.keys(target).length == 0) {
return target;
}
function _clone(b, a) {
var nextBatch = [];
for (var key in b) {
if (typeof b[key] === 'object' && b[key] !== null) {
if (b[key] instanceof Array) {
a[key] = [];
}
else {
a[key] = {};
}
nextBatch.push(_clone.bind(null, b[key], a[key]));
}
else {
a[key] = b[key];
}
}
return nextBatch;
};
var ret = target instanceof Array ? [] : {};
(trampoline.bind(null, _clone))(target, ret);
return ret;
};
扩展操作器... (原始序列 - 仅) 序列(0) (原始序列 - 仅) 序列() (原始序列 - 仅) concat() (原始序列 - 仅) 定制功能,如下所示(每个序列) jQuery 的 $.extend() (每个序列) JSON.parse(JSON.stringify()) (原始和字面序列 - 仅) Underscore 的 _.clone() (原始和字面序列 - 仅) Lodash 的 _.cloneDeep() (每个序列)
let arr1a = [1, 'a', true];
let arr1b = [...arr1a];
而且在哪裡 slice() 比 concat( 有更好的性能: https://jsbench.me/x5ktn7o94d/
let arr1c = arr1a.splice(0);
let arr1d = arr1a.slice();
let arr1e = arr1a.concat();
let arr2a = [1, 'a', true, {}, []];
let arr2b = JSON.parse(JSON.stringify(arr2a));
let arr3a = [1, 'a', true, {}, [], new Object()];
function copy(aObject) {
// Prevent undefined objects
// if (!aObject) return aObject;
let bObject = Array.isArray(aObject) ? [] : {};
let value;
for (const key in aObject) {
// Prevent self-references to parent object
// if (Object.is(aObject[key], aObject)) continue;
value = aObject[key];
bObject[key] = (typeof value === "object") ? copy(value) : value;
}
return bObject;
}
let arr3b = copy(arr3a);
或使用第三方实用功能:
let arr3c = $.extend(true, [], arr3a); // jQuery Extend
let arr3d = _.cloneDeep(arr3a); // Lodash
注意: jQuery 的 $.extend 也比 JSON.parse(JSON.stringify() 表现更好):
对于未来的参考,可以使用此代码
第6章:
_clone: function(obj){
let newObj = {};
for(let i in obj){
if(typeof(obj[i]) === 'object' && Object.keys(obj[i]).length){
newObj[i] = clone(obj[i]);
} else{
newObj[i] = obj[i];
}
}
return Object.assign({},newObj);
}
第5章:
function clone(obj){
let newObj = {};
for(let i in obj){
if(typeof(obj[i]) === 'object' && Object.keys(obj[i]).length){
newObj[i] = clone(obj[i]);
} else{
newObj[i] = obj[i];
}
}
return Object.assign({},newObj);
) )
E.G
var obj ={a:{b:1,c:3},d:4,e:{f:6}}
var xc = clone(obj);
console.log(obj); //{a:{b:1,c:3},d:4,e:{f:6}}
console.log(xc); //{a:{b:1,c:3},d:4,e:{f:6}}
xc.a.b = 90;
console.log(obj); //{a:{b:1,c:3},d:4,e:{f:6}}
console.log(xc); //{a:{b:90,c:3},d:4,e:{f:6}}
没有触摸原型遗产,你可以如下深孤独的物体和岩石;
函数 objectClone(o){ var ot = Array.isArray(o); return o!== null && typeof o === “object”? Object.keys(o).reduce((r,k) => o[k]!== null && typeof o[k] === “object”? (r[k] = objectClone(o[k]),r) : (r[k] = o[k],r), ot?