clone(obj)
replit ⟩ JS ⟩ object ⟩ clone()
// truly exact copy of `obj`, including all properties:
// • enumerable and non-enumerable
// • data properties, setters/getters
// with the right [[Prototype]].
function clone(obj) {
return Object.create(
Object.getPrototypeOf(obj), // same [[Prototype]] as obj.
Object.getOwnPropertyDescriptors(obj) // clone all own members.
);
}💈範例：
雖然可以用 clone() 複製物件，但兩個物件之間，依然有可能存在些微差異，例如：下例的 a 是一個 Array，但 clone() 之後的 a2 就不是 Array❗️
// an array
let a = [1,2,3];
// an object
const o = {
name: 'Joe',
age: 25,
array: [1,2,3],
hobbies: {
sports: ['badminton', 'baseball'],
games: ['zelda', 'poker']
}
}
// clone
let a2 = clone(a);
let o2 = clone(o);
// change some properties
o.array = []; // ⭐ now, `o.array !== o2.array`❗
o.hobbies.games = []; // ⭐ since `o.hobbies === o2.hobbies`,
// `o.hobbies.games === o2.hobbies.games`❗
// ---------------------- console ----------------------------------
[
a, // [ 1, 2, 3 ]
typeof a, // 'object'
Array.isArray(a), // true
a2, // Array { '0': 1, '1': 2, '2': 3 }
typeof a2, // 'object'
Array.isArray(a2), // false (a2 is NOT an array❗)
JSON.stringify(o),
// {
// name: "Joe",
// age : 25,
// array : [], // ⭐ `o.array` overwritten❗
// hobbies: {
// sports:["badminton","baseball"],
// games :[] // ⭐ this one has changed.
// }
// }
JSON.stringify(o2),
// {
// name: "Joe",
// age : 25,
// array : [1,2,3], // ⭐ `o2.array` remains intact.
// hobbies: {
// sports:["badminton","baseball"],
// games :[] // ⭐ this (same) one has changed too.
// }
// }
].forEach(x => log(x));let arr = [1, 2, 3];
// ⭐️ shallow copy
let copy = [...arr]; // "spread" operator
let copy = arr.slice() // Array method
// ⭐️ deep copy
let deepcopy = JSON.parse(JSON.stringify(arr));Last updated