➕nullish coalescing (??)

🚧 under construction

JS ⟩ statement ⟩ expression ⟩ operator ⟩ logical ⟩ nullish coalescing operator (??)

(⭐️ ES2020)

expr ?? default    // nullish coalescing

👉 table of operators

⭐️ 重點

?? operator

• the precedence of ?? relative to ||, && is not defined.

• explicitly use parentheses if ?? is mixed with ||, &&.

👉 table of operators

👥 相關

• nullish means null or undefined.

• conditional operator (?:)

• ?? may be used after optional chaining (?., ?.[]) to provide a default value.

• logical operator

💈範例

// ⭐️ nullish coalescing
x = x ?? 100;

// polyfill
x = (x !== undefined && x !== null) ? x : 100;

// ❗️ slightly different from:
x = x || 100;

📗 參考

• JS.info ⟩ polyfill ⟩ transpiler

📘 手冊

• Nullish coalescing operator (??)

❓

問：「 Google Apps Script 支援 nullish coalescing 嗎？」

答：「 測試過，看來是支援的。」

🚧

• ||

• &&