(Следующее было главным образом интеграция @ Мацей Буковски , @ А. Леви , @ Ян Туро , @ Реду и ответы @ LeviRoberts , @ RobG , большое им спасибо !!!)
Глубокая копия ? - ДА! (В основном);
Мелкая копия ? - НЕТ! (кроме Proxy).
Искренне приветствую всех на тестировании clone().
Кроме того, defineProp() предназначен для простого и быстрого (пере) определения или копирования любого типа дескриптора.
Функция
function clone(object) {
/*
Deep copy objects by value rather than by reference,
exception: `Proxy`
*/
const seen = new WeakMap()
return (function clone(object) {
if (object !== Object(object)) return object /*
—— Check if the object belongs to a primitive data type */
if (object instanceof Node) return object.cloneNode(true) /*
—— Clone DOM trees */
let _object // The clone of object
switch (object.constructor) {
case Object:
case Array:
_object = cloneObject(object)
break
case Date:
_object = new Date(+object)
break
case Function:
const fnStr = String(object)
_object = new Function("return " +
(/^(?!function |[^{]+?=>)[^(]+?\(/.test(fnStr)
? "function " : ""
) + fnStr
).call(object)
Object.defineProperties(_object,
Object.getOwnPropertyDescriptors(object)
)
break
default:
switch (Object.prototype.toString.call(object.constructor)) {
// // Stem from:
case "[object Function]": // `class`
case "[object Undefined]": // `Object.create(null)`
_object = cloneObject(object)
break
default: // `Proxy`
_object = object
}
}
return _object
function cloneObject(object) {
if (seen.has(object)) return seen.get(object) /*
—— Handle recursive references (circular structures) */
const _object = Array.isArray(object)
? []
: Object.create(Object.getPrototypeOf(object)) /*
—— Assign [[Prototype]] for inheritance */
seen.set(object, _object) /*
—— Make `_object` the associative mirror of `object` */
Reflect.ownKeys(object).forEach(key =>
defineProp(_object, key, { value: clone(object[key]) }, object)
)
return _object
}
})(object)
}
function defineProp(object, key, descriptor = {}, copyFrom = {}) {
const prevDesc = Object.getOwnPropertyDescriptor(object, key)
|| { configurable: true, writable: true }
, copyDesc = Object.getOwnPropertyDescriptor(copyFrom, key)
|| { configurable: true, writable: true } // Custom…
|| {} // …or left to native default settings
const { configurable: _configurable, writable: _writable } = prevDesc
, test = _writable === undefined
? _configurable // Can redefine property
: _configurable && _writable // Can assign to property
if (!test || arguments.length <= 2) return test;
["get", "set", "value", "writable", "enumerable", "configurable"]
.forEach(k =>
descriptor[k] === undefined && (descriptor[k] = copyDesc[k])
)
const { get, set, value, writable, enumerable, configurable }
= descriptor
return Object.defineProperty(object, key, {
enumerable, configurable, ...get || set
? { get, set } // Accessor descriptor
: { value, writable } // Data descriptor
})
}
// Тесты
"use strict"
const obj0 = {
u: undefined,
nul: null,
t: true,
n: 9,
str1: "string",
str2: "",
sym: Symbol("symbol"),
[Symbol("e")]: Math.E,
f: {
getAccessorStr(object) {
return []
.concat(...
Object.values(Object.getOwnPropertyDescriptors(object))
.filter(desc => desc.writable === undefined)
.map(desc => Object.values(desc))
)
.filter(prop => typeof prop === "function")
.map(String)
},
f0: function f0() { },
f1: function () { },
f2: a => a / (a + 1),
f3: () => 0,
f4(params) { return param => param + params },
f5: (a, b) => ({ c = 0 } = {}) => a + b + c
},
o: {
n: 0,
o: {
f: function (...args) { }
}
},
arr: [[0], [1, 2]],
d: new Date(),
get g() { return 0 }
}
defineProp(obj0, "s", {
set(v) { this._s = v }
})
defineProp(obj0.arr, "tint", {
value: { is: "non-enumerable" }
})
obj0.arr[0].name = "nested array"
let obj1 = clone(obj0)
obj1.o.n = 1
obj1.o.o.g = function g(a = 0, b = 0) { return a + b }
obj1.arr[1][1] = 3
obj1.d.setTime(+obj0.d + 60 * 1000)
obj1.arr.tint.is = "enumerable? no"
obj1.arr[0].name = "a nested arr"
defineProp(obj1, "s", {
set(v) { this._s = v + 1 }
})
console.log("\n\n" + "-".repeat(2 ** 6))
console.log(">:>: Test - Routinely")
console.log("obj0:\n ", JSON.stringify(obj0))
console.log("obj1:\n ", JSON.stringify(obj1))
console.log()
console.log("obj0:\n ", obj0)
console.log("obj1:\n ", obj1)
console.log()
console.log("obj0\n ",
".arr.tint:", obj0.arr.tint, "\n ",
".arr[0].name:", obj0.arr[0].name
)
console.log("obj1\n ",
".arr.tint:", obj1.arr.tint, "\n ",
".arr[0].name:", obj1.arr[0].name
)
console.log()
console.log("Accessor-type descriptor\n ",
"of obj0:", obj0.f.getAccessorStr(obj0), "\n ",
"of obj1:", obj1.f.getAccessorStr(obj1), "\n ",
"set (obj0 & obj1) .s :", obj0.s = obj1.s = 0, "\n ",
" → (obj0 , obj1) ._s:", obj0._s, ",", obj1._s
)
console.log("—— obj0 has not been interfered.")
console.log("\n\n" + "-".repeat(2 ** 6))
console.log(">:>: Test - Circular structures")
obj0.o.r = {}
obj0.o.r.recursion = obj0.o
obj0.arr[1] = obj0.arr
obj1 = clone(obj0)
console.log("obj0:\n ", obj0)
console.log("obj1:\n ", obj1)
console.log("Clear obj0's recursion:",
obj0.o.r.recursion = null, obj0.arr[1] = 1
)
console.log(
"obj0\n ",
".o.r:", obj0.o.r, "\n ",
".arr:", obj0.arr
)
console.log(
"obj1\n ",
".o.r:", obj1.o.r, "\n ",
".arr:", obj1.arr
)
console.log("—— obj1 has not been interfered.")
console.log("\n\n" + "-".repeat(2 ** 6))
console.log(">:>: Test - Classes")
class Person {
constructor(name) {
this.name = name
}
}
class Boy extends Person { }
Boy.prototype.sex = "M"
const boy0 = new Boy
boy0.hobby = { sport: "spaceflight" }
const boy1 = clone(boy0)
boy1.hobby.sport = "superluminal flight"
boy0.name = "one"
boy1.name = "neo"
console.log("boy0:\n ", boy0)
console.log("boy1:\n ", boy1)
console.log("boy1's prototype === boy0's:",
Object.getPrototypeOf(boy1) === Object.getPrototypeOf(boy0)
)
Ссылки
Object.create() | MDN Object.defineProperties() | MDN - Перечислимость и владение недвижимостью | MDN
- TypeError: значение циклического объекта | MDN
Используемые языковые трюки
- Условно добавить объект на объект