JSON
const copy = JSON.parse(JSON.stringify(a));
缺点
- 不支持 Date、正则、undefined、函数等数据
- 不支持引用，即环状结构
递归
要点：
- 判断类型 => instanceof
- 检查环 => 使用哈希表缓存
- 不拷贝原型上的属性 => hasOwnPropertype
const deepCopy = (a, cache) => {
if (!cache) {
cache = new Map();
}
// 不考虑跨 iframe
if (a instanceof Object) {
if (cache.get(a)) {
return cache.get(a);
}
let result = null;
if (a instanceof Function) {
// 有 prototype 就是普通函数
if (a.prototype) {
result = function () {
return a.apply(this, arguments);
}
} else {
result = (...args) => {
return a.call(undefined, ...args);
}
}
} else if (a instanceof Array) {
result = [];
} else if (a instanceof Date) {
result = new Date(a - 0);
} else if (a instanceof RegExp) {
result = new RegExp(a.source, a.flags);
} else {
result = {};
}
cache.set(a, result);
for (let key in a) {
if (a.hasOwnProperty(key)) {
result[key] = deepCopy(a[key], cache);
}
}
return result;
}
return a;
}
const a = {
number: 1, bool: false, str: 'hi', empty1: undefined, empty2: null,
array: [
{name: 'frank', age: 18},
{name: 'jacky', age: 19}
],
date: new Date(2000, 0, 1, 20, 30, 0),
regex: /\.(j|t)sx/i,
obj: {name: 'frank', age: 18},
f1: (a, b) => a + b,
f2: function (a, b) { return a + b }
}
a.self = a;
const b = deepCopy(a);
console.log(b.self === b); // true
b.self = 'hi'
console.log(a.self !== 'hi'); //true
