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
Shallow copy one-lineer (ECMAScript 第五版):
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
并下载单线复制(ECMAScript 第六版,2015年):
var origin = { foo : {} };
var copy = Object.assign({}, origin);
console.log(origin, copy);
console.log(origin == copy); // false
console.log(origin.foo == copy.foo); // true
其他回答
只有在您可以使用 ECMAScript 6 或 transpilers 时。
特性:
将不会在复制时发射输入/输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输入输
代码:
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;
}
我知道这是一个古老的帖子,但我以为这可能有助于下一个人,谁在跳动。
只要你不分配一个对象到任何东西,它保留没有参考在记忆中,所以要创建一个对象,你想在其他对象中分享,你将不得不创建一个工厂如下:
var a = function(){
return {
father:'zacharias'
};
},
b = a(),
c = a();
c.father = 'johndoe';
alert(b.father);
Shallow copy one-lineer (ECMAScript 第五版):
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
并下载单线复制(ECMAScript 第六版,2015年):
var origin = { foo : {} };
var copy = Object.assign({}, origin);
console.log(origin, copy);
console.log(origin == copy); // false
console.log(origin.foo == copy.foo); // true
这通常不是最有效的解决方案,但它是我需要的。
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;
}
自行车测试...
a = []
a.push("b", "c", a)
aa = clone(a)
aa === a //=> false
aa[2] === a //=> false
aa[2] === a[2] //=> false
aa[2] === aa //=> true
功能测试...
f = new Function
f.a = a
ff = clone(f)
ff === f //=> true
ff.a === a //=> false
下面是同一个对象的两个例子,我发现了它,目前正在使用它,它很简单,易于使用。
var objToCreate = JSON.parse(JSON.stringify(cloneThis));