Design PatternsPrototype cho phép copy (clone) object hiện có mà không phụ thuộc vào class của nó — tạo object mới bằng cách sao chép prototype. JavaScript đặc biệt phù hợp vì có prototype-based inheritance tự nhiên.
Ví dụ: const config = { timeout: 3000, retries: 3 }; const apiConfig = { ...config, baseURL: '/api' } — spread operator là Shallow Prototype. Dùng khi: khởi tạo object tốn kém (DB query, file I/O) và muốn clone thay vì tạo mới; khi có nhiều preset configuration chỉ khác nhau vài thuộc tính. Chú ý Shallow vs Deep clone: Object.assign() và spread {...} chỉ shallow clone, object nested vẫn shared reference — dùng structuredClone() (ES2022) hoặc JSON.parse(JSON.stringify()) cho deep clone. Không dùng khi object có circular reference hoặc function (JSON.stringify sẽ mất).
Prototype allows cloning an existing object without depending on its class — creating new objects by copying a prototype. JavaScript is especially well-suited for this because of its native prototype-based inheritance.
Example: const config = { timeout: 3000, retries: 3 }; const apiConfig = { ...config, baseURL: '/api' } — the spread operator is a shallow Prototype clone. Use it when object initialization is expensive (DB queries, file I/O) and you'd rather clone than recreate; or when you have many preset configurations that differ by only a few properties. Be aware of shallow vs deep clone: Object.assign() and spread {...} only shallow clone, so nested objects still share references — use structuredClone() (ES2022) or JSON.parse(JSON.stringify()) for deep clones. Avoid it when objects have circular references or functions, since JSON.stringify will lose those.