Provide a Type for this in Callbacks if It's Part of Their API

Overview

When a library calls a user-provided callback with a specific this context, that context is part of the API. TypeScript allows you to type this as the first parameter of a function, even though it's not a real parameter. This documents and enforces the expected context.

When to Use This Skill

• Callbacks use this
• API provides this context
• Typing event handlers
• Library sets this in callbacks
• Documenting callback context

The Iron Rule

Type this as the first parameter when it's part of your callback API. This documents the expected context and enables autocompletion.

Example