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

这是我创建的最快的方法,不使用原型,所以它将保持在新对象中拥有自己的所有权。

解决方案是对原件的顶级属性进行 iterate,创建两个副本,从原件中删除每个属性,然后重新设置原件并返回新副本,它只需要像顶级属性一样多次 iterate。

唯一的缺点是,原始对象必须配备其原创创建的名称空间,以便重新设置。

copyDeleteAndReset:function(namespace,strObjName){
    var obj = namespace[strObjName],
    objNew = {},objOrig = {};
    for(i in obj){
        if(obj.hasOwnProperty(i)){
            objNew[i] = objOrig[i] = obj[i];
            delete obj[i];
        }
    }
    namespace[strObjName] = objOrig;
    return objNew;
}

var namespace = {};
namespace.objOrig = {
    '0':{
        innerObj:{a:0,b:1,c:2}
    }
}

var objNew = copyDeleteAndReset(namespace,'objOrig');
objNew['0'] = 'NEW VALUE';

console.log(objNew['0']) === 'NEW VALUE';
console.log(namespace.objOrig['0']) === innerObj:{a:0,b:1,c:2};

其他回答

class Handler { static deepCopy (obj) { if (Object.prototype.toString.call(obj) === '[object Array]') { const result = []; for (let i = 0, len = obj.length; i < len; i++) { result[i] = Handler.deepCopy(obj[i]); } return result; } else if (Object.prototype.toString.call(obj) === '[object Object]') { const result = {}; for (let prop in obj) { result[prop] = Handler.deepCopy(obj[prop]); } return result; } return obj; } }

结构化克隆

HTML 标准包含一个内部结构化的克隆/序列化算法,可以创建对象的深度克隆,它仍然仅限于某些内置类型,但除了由 JSON 支持的少数类型之外,它还支持日期、RegExps、地图、套件、Blobs、FileLists、ImageDatas、Sparse Arrays、Typed Arrays等。

结构化Clone 全球功能由 Node 17.0 提供:

const clone = structuredClone(original);

以前版本: Node.js 的 v8 模块(如 Node 11 )直接展示了结构化序列化 API,但此功能仍然被标记为“实验性”,并在未来的版本中可更改或删除。

const v8 = require('v8');

const structuredClone = obj => {
  return v8.deserialize(v8.serialize(obj));
};

直接支持浏览器:可用于Firefox 94

const clone = structuredClone(original);

class StructuredCloner {
  constructor() {
    this.pendingClones_ = new Map();
    this.nextKey_ = 0;
    
    const channel = new MessageChannel();
    this.inPort_ = channel.port1;
    this.outPort_ = channel.port2;
    
    this.outPort_.onmessage = ({data: {key, value}}) => {
      const resolve = this.pendingClones_.get(key);
      resolve(value);
      this.pendingClones_.delete(key);
    };
    this.outPort_.start();
  }

  cloneAsync(value) {
    return new Promise(resolve => {
      const key = this.nextKey_++;
      this.pendingClones_.set(key, resolve);
      this.inPort_.postMessage({key, value});
    });
  }
}

const structuredCloneAsync = window.structuredCloneAsync =
    StructuredCloner.prototype.cloneAsync.bind(new StructuredCloner);

const main = async () => {
  const original = { date: new Date(), number: Math.random() };
  original.self = original;

  const clone = await structuredCloneAsync(original);

  // They're different objects:
  console.assert(original !== clone);
  console.assert(original.date !== clone.date);

  // They're cyclical:
  console.assert(original.self === original);
  console.assert(clone.self === clone);

  // They contain equivalent values:
  console.assert(original.number === clone.number);
  console.assert(Number(original.date) === Number(clone.date));
  
  console.log("Assertions complete.");
};

main();

const structuredClone = obj => {
  const oldState = history.state;
  history.replaceState(obj, null);
  const clonedObj = history.state;
  history.replaceState(oldState, null);
  return clonedObj;
};

雖然同步,但這可能非常慢。 它發生了所有與操縱瀏覽器歷史相關的頭部. 重複召喚這種方法可能會導致Chrome暫時變成無責任。

const structuredClone = obj => {
  const n = new Notification('', {data: obj, silent: true});
  n.onshow = n.close.bind(n);
  return n.data;
};

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

有很多答案,但没有一个给了我需要的效果,我想利用jQuery的深复制的力量......但是,当它进入一个序列时,它只是复制了对序列的参考,并深复制了其中内容。

(它甚至检查 kendo.data.ObservableArray 如果你想要它! 但是, 确保你打电话 kendo.observable(newItem) 如果你想 Arrays 再次可观察。

所以,要完全复制一个现有项目,你只是这样做:

var newItem = jQuery.extend(true, {}, oldItem);
createNewArrays(newItem);


function createNewArrays(obj) {
    for (var prop in obj) {
        if ((kendo != null && obj[prop] instanceof kendo.data.ObservableArray) || obj[prop] instanceof Array) {
            var copy = [];
            $.each(obj[prop], function (i, item) {
                var newChild = $.extend(true, {}, item);
                createNewArrays(newChild);
                copy.push(newChild);
            });
            obj[prop] = copy;
        }
    }
}

对于想要使用 JSON.parse(JSON.stringify(obj)) 版本的人,但没有失去日期对象,您可以使用 Parse 方法的第二个论点将行转换为日期:

function clone(obj) { var regExp = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/; return JSON.parse(JSON.stringify(obj), function(k, v) { if (typeof v === 'string' && regExp.test(v)) return new Date(v) return v; }) } // usage: var original = { a: [1, null, undefined, 0, {a:null}, new Date()], b: { c(){ return 0 } } } var cloned = clone(original) console.log(cloned)