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
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;
};
其他回答
单线 ECMAScript 6 解决方案(特殊对象类型如 Date/Regex 未处理):
const clone = (o) => typeof o === 'object' && o!== null? // only clone objects (Array.isArray(o)? // if cloning an array o.map(e => clone(e)) : // clone each of its elements Object.keys(o).reduce( // otherwise reduce every key in the object (r, k) => (r[k] = clone(o[k]), r), {} // and save its cloned value
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。
希望这能帮助。
function deepClone(obj) {
/*
* Duplicates an object
*/
var ret = null;
if (obj !== Object(obj)) { // primitive types
return obj;
}
if (obj instanceof String || obj instanceof Number || obj instanceof Boolean) { // string objecs
ret = obj; // for ex: obj = new String("Spidergap")
} else if (obj instanceof Date) { // date
ret = new obj.constructor();
} else
ret = Object.create(obj.constructor.prototype);
var prop = null;
var allProps = Object.getOwnPropertyNames(obj); //gets non enumerables also
var props = {};
for (var i in allProps) {
prop = allProps[i];
props[prop] = false;
}
for (i in obj) {
props[i] = i;
}
//now props contain both enums and non enums
var propDescriptor = null;
var newPropVal = null; // value of the property in new object
for (i in props) {
prop = obj[i];
propDescriptor = Object.getOwnPropertyDescriptor(obj, i);
if (Array.isArray(prop)) { //not backward compatible
prop = prop.slice(); // to copy the array
} else
if (prop instanceof Date == true) {
prop = new prop.constructor();
} else
if (prop instanceof Object == true) {
if (prop instanceof Function == true) { // function
if (!Function.prototype.clone) {
Function.prototype.clone = function() {
var that = this;
var temp = function tmp() {
return that.apply(this, arguments);
};
for (var ky in this) {
temp[ky] = this[ky];
}
return temp;
}
}
prop = prop.clone();
} else // normal object
{
prop = deepClone(prop);
}
}
newPropVal = {
value: prop
};
if (propDescriptor) {
/*
* If property descriptors are there, they must be copied
*/
newPropVal.enumerable = propDescriptor.enumerable;
newPropVal.writable = propDescriptor.writable;
}
if (!ret.hasOwnProperty(i)) // when String or other predefined objects
Object.defineProperty(ret, i, newPropVal); // non enumerable
}
return ret;
}
HTTPS://github.com/jinujd/Javascript-Deep-Clone
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}}
什么是无与伦比的对象克隆,由一个承诺完成?
async function clone(thingy /**/)
{
if(thingy instanceof Promise)
{
throw Error("This function cannot clone Promises.");
}
return thingy;
}