Avoid Object Wrapper Types (String, Number, Boolean, Symbol, BigInt)

Overview

Use lowercase primitive types, never uppercase wrapper types.

JavaScript has primitive types (string, number, boolean) and object wrapper types (String, Number, Boolean). TypeScript has types for both, but you should almost never use the wrapper types.

When to Use This Skill

• Typing any primitive value
• Seeing errors about wrapper type mismatches
• Understanding why String !== string
• Working with methods on primitives

The Iron Rule