js对象clone

1. 浅拷贝,如果对象的属性值是数或者字符串则值传递，否则为引用传递

function clone(obj){
    return {...obj};
}
or
function clone(obj){
    return Object.assign({},obj);
}

var t1 = {a: 'hello', b:[0, 1]}
var t2 = clone(t1);
t1.a = 'world';
console.log(t1.a, t2.a); // world hello
t1.b[0] = -1
console.log(t1.b[0], t2.b[0]); // -1 -1

2. deepClone

function clone(obj) {
    var newobj = obj.constructor === Array ? [] : {};
    if (typeof obj !== "object") {
        return obj;
    } else {
        for (var i in obj) {
            newobj[i] = typeof obj[i] === "object" ? clone(obj[i]) : obj[i];
        }
    }
    return newobj;
}

• 在存在Symbol类型属性key时，无法正确拷贝

function clone(obj) {
    return JSON.parse(JSON.stringify(obj);
}

• Set 类型、Map 类型以及 Buffer 类型会被转换成 {}
• undefined、任意的函数以及 symbol 值，在序列化过程中会被忽略（出现在非数组对象的属性值中时）或者被转换成 null（出现在数组中时）
• 对包含循环引用的对象（对象之间相互引用，形成无限循环）执行此方法，会抛出错误

3. 结构化克隆,第一种推荐，参考JavaScript 深拷贝性能分析

function StructuredClone(param) {
  return new Promise(function (res, rej) {
    const {port1, port2} = new MessageChannel();
    port2.onmessage = ev => res(ev.data);
    port1.postMessage(param);
  })
}
StructuredClone(objects).then(result => console.log(result))

function structuralClone(obj) {
  const oldState = history.state;
  history.replaceState(obj, document.title);
  const copy = history.state;
  history.replaceState(oldState, document.title);
  return copy;
}
const clone = structuralClone(objects);

function structuralClone(obj) {
  return new Notification('', {data: obj, silent: true}).data;
}

const obj = /* ... */;
const clone = structuralClone(obj);