克隆与合并——展开语法和 Object.assign

// Shallow clone with object spread
const user = { name: "Ayla", level: 1 };
const clone = { ...user };

clone.level = 2;

console.log("Original:", user);
console.log("Clone:", clone);

// Shallow clone with Object.assign
const settings = { theme: "dark", compact: false };
const copy = Object.assign({}, settings);

copy.compact = true;

console.log("Settings:", settings);
console.log("Copy:", copy);

// Merge: later keys overwrite earlier ones
const base = { a: 1, b: 2 };
const extra = { b: 9, c: 3 };

const mergedSpread = { ...base, ...extra };
const mergedAssign = Object.assign({}, base, extra);

console.log("Spread merged:", mergedSpread);
console.log("Assign merged:", mergedAssign);

// Arrays: clone and merge with spread
const nums = [1, 2, 3];
const cloneNums = [...nums];

const more = [4, 5];
const mergedNums = [...nums, ...more];

console.log("nums:", nums);
console.log("clone:", cloneNums);
console.log("merged:", mergedNums);

// Shallow copy caveat: nested objects are shared
const original = { user: { name: "Mina" }, active: true };
const shallow = { ...original };

// Mutate nested object
shallow.user.name = "Lena";

console.log("Original:", original);
console.log("Shallow:", shallow);