…每个对象在同一个数组中也有对其他对象的引用?

当我第一次想到这个问题的时候,我就想到了

var clonedNodesArray = nodesArray.clone()

并搜索如何在JavaScript中克隆对象的信息。我确实在Stack Overflow上找到了一个问题(同样由@JohnResig回答),他指出用jQuery你可以做到

var clonedNodesArray = jQuery.extend({}, nodesArray);

克隆对象。虽然我尝试了这个,但这只复制了数组中对象的引用。如果我

nodesArray[0].value = "red"
clonedNodesArray[0].value = "green"

nodesArray[0]和clonedNodesArray[0]的值将显示为“绿色”。然后我尝试了

var clonedNodesArray = jQuery.extend(true, {}, nodesArray);

它深度复制了一个对象,但我分别从Firebug和Opera Dragonfly得到了“太多递归”和“控制堆栈溢出”的消息。

你会怎么做?这是不应该做的事情吗?在JavaScript中是否有可重用的方法来做到这一点?


当前回答

如果您想实现深度克隆,请使用JSON.parse(JSON. parse)。Stringify(你的{}或[])):

const myObj ={ 答:1, 乙: 2, 乙: 3 } const deepClone = JSON.parse(JSON.stringify(myObj)); 深度克隆 = 12; console.log(“deepClone-----”+myObj.a); const withOutDeepClone = myObj; 没有OutDeepClone.a = 12; console.log(“withOutDeepClone----” + myObj.a);

其他回答

我可能有一种简单的方法来做到这一点,而不需要做痛苦的递归,也不知道有关对象的所有细节。使用jQuery,只需使用jQuery $. tojson (myObjectArray)将对象转换为JSON,然后将JSON字符串计算回对象。砰!搞定了,搞定了!问题解决了。:)

var oldObjArray = [{ Something: 'blah', Cool: true }];
var newObjArray = eval($.toJSON(oldObjArray));

如果你只需要一个浅拷贝,一个非常简单的方法是:

new_array = old_array.slice(0);
var game_popularity = [
     { game: "fruit ninja", popularity: 78 },
     { game: "road runner", popularity: 20 },
     { game: "maze runner", popularity: 40 },
     { game: "ludo", popularity: 75 },
     { game: "temple runner", popularity: 86 }
];
console.log("sorted original array before clonning");
game_popularity.sort((a, b) => a.popularity < b.popularity);
console.log(game_popularity);


console.log("clone using object assign");
const cl2 = game_popularity.map(a => Object.assign({}, a));
cl2[1].game = "clash of titan";
cl2.push({ game: "logan", popularity: 57 });
console.log(cl2);


// Adding new array element doesnt reflect in original array
console.log("clone using concat");
var ph = []
var cl = ph.concat(game_popularity);

// Copied by reference ?
cl[0].game = "rise of civilization";

game_popularity[0].game = 'ping me';
cl.push({ game: "angry bird", popularity: 67 });
console.log(cl);

console.log("clone using ellipses");
var cl3 = [...game_popularity];
cl3.push({ game: "blue whale", popularity: 67 });
cl3[2].game = "harry potter";
console.log(cl3);

console.log("clone using json.parse");
var cl4 = JSON.parse(JSON.stringify(game_popularity));
cl4.push({ game: "home alone", popularity: 87 });
cl4[3].game ="lockhead martin";
console.log(cl4);

console.log("clone using Object.create");
var cl5 = Array.from(Object.create(game_popularity));
cl5.push({ game: "fish ville", popularity: 87 });
cl5[3].game ="veto power";
console.log(cl5);


// Array function
console.log("sorted original array after clonning");
game_popularity.sort((a, b) => a.popularity < b.popularity);
console.log(game_popularity);


console.log("Object.assign deep clone object array");
console.log("json.parse deep clone object array");
console.log("concat does not deep clone object array");
console.log("ellipses does not deep clone object array");
console.log("Object.create does not deep clone object array");

输出

sorted original array before clonning
[ { game: 'temple runner', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'ludo', popularity: 75 },
{ game: 'maze runner', popularity: 40 },
{ game: 'road runner', popularity: 20 } ]
clone using object assign
[ { game: 'temple runner', popularity: 86 },
{ game: 'clash of titan', popularity: 78 },
{ game: 'ludo', popularity: 75 },
{ game: 'maze runner', popularity: 40 },
{ game: 'road runner', popularity: 20 },
{ game: 'logan', popularity: 57 } ]
clone using concat
[ { game: 'ping me', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'ludo', popularity: 75 },
{ game: 'maze runner', popularity: 40 },
{ game: 'road runner', popularity: 20 },
{ game: 'angry bird', popularity: 67 } ]
clone using ellipses
[ { game: 'ping me', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'harry potter', popularity: 75 },
{ game: 'maze runner', popularity: 40 },
{ game: 'road runner', popularity: 20 },
{ game: 'blue whale', popularity: 67 } ]
clone using json.parse
[ { game: 'ping me', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'harry potter', popularity: 75 },
{ game: 'lockhead martin', popularity: 40 },
{ game: 'road runner', popularity: 20 },
{ game: 'home alone', popularity: 87 } ]
clone using Object.create
[ { game: 'ping me', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'harry potter', popularity: 75 },
{ game: 'veto power', popularity: 40 },
{ game: 'road runner', popularity: 20 },
{ game: 'fish ville', popularity: 87 } ]
sorted original array after clonning
[ { game: 'ping me', popularity: 86 },
{ game: 'fruit ninja', popularity: 78 },
{ game: 'harry potter', popularity: 75 },
{ game: 'veto power', popularity: 40 },
{ game: 'road runner', popularity: 20 } ]

Object.assign deep clone object array
json.parse deep clone object array
concat does not deep clone object array
ellipses does not deep clone object array
Object.create does not deep clone object array

正如Daniel Lew提到的,循环图有一些问题。如果我有这个问题,我要么向有问题的对象添加特殊的clone()方法,要么记住我已经复制了哪些对象。

我会用一个变量copyCount来做,它在你每次复制代码时增加1。copyCount小于当前复制进程的对象将被复制。如果不是,则应该引用已经存在的副本。这就需要从原文链接到副本。

还有一个问题:内存。如果您从一个对象引用到另一个对象,那么浏览器很可能无法释放这些对象,因为它们总是从某个地方引用。您必须进行第二次传递,将所有复制引用设置为Null。(如果你这样做,你不必有一个copyCount,但一个布尔iscopy就足够了,因为你可以在第二步重置值。)

我之所以回答这个问题,是因为似乎没有一个简单而明确的解决方案来解决“在JavaScript中克隆对象数组”的问题:

function deepCopy (arr) {
    var out = [];
    for (var i = 0, len = arr.length; i < len; i++) {
        var item = arr[i];
        var obj = {};
        for (var k in item) {
            obj[k] = item[k];
        }
        out.push(obj);
    }
    return out;
}

// test case

var original = [
    {'a' : 1},
    {'b' : 2}
    ];

var copy = deepCopy(original);

// change value in copy
copy[0]['a'] = 'not 1';

// original[0]['a'] still equals 1

该解决方案迭代数组值,迭代对象键,将后者保存到一个新对象,并将该新对象推入到一个新数组。

看到jsfiddle。注意:简单的.slice()或[].concat()对于数组中的对象是不够的。