iterate-objects-safely

SKILL.md

Iterating over objects in TypeScript is surprisingly tricky. The for...in loop infers keys as string rather than the object's keys, leading to indexing errors. This happens because objects can have additional properties beyond their declared type (structural typing), and for...in includes inherited properties.

Understanding safe iteration patterns helps you avoid any types and type assertions while correctly handling object traversal.

Use Object.entries for safe iteration over any object. Use for...in with keyof assertions only when you know the exact shape. Consider Map for guaranteed type safety.

在迭代對象鍵和值時使用。當 for...in 循環產生類型錯誤時使用。當 Object.entries 返回任何類型時使用。在處理原型污染問題時使用。在考慮地圖與對象時使用。 來源：marius-townhouse/effective-typescript-skills。

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