Object.assign() và spread operator khi copy object khác nhau như thế nào?

Cả hai đều shallow copy. Object.assign() copy vào object đích hiện có, trigger setters trên target. Spread tạo plain object mới, không trigger setters.

Object.assign() copy enumerable own properties bao gồm cả Symbol. Với nested objects, cả hai chỉ copy reference, không deep copy.

const target = { a: 1 };
const result = Object.assign(target, { b: 2 }); // mutates target
const spread = { ...target, c: 3 };             // new object

Both perform shallow copies. Object.assign() copies into an existing target object and triggers setters on the target. Spread creates a new plain object without triggering setters.

Object.assign() copies enumerable own properties including Symbols. For nested objects, both only copy the reference — neither performs a deep copy.

const target = { a: 1 };
const result = Object.assign(target, { b: 2 }); // mutates target
const spread = { ...target, c: 3 };             // new object