functions.md

Functions

Event Handlers

• Type the event handler, not the callback.

  Why? Provides better code completion. This can be removed when microsoft/TypeScript#8134 lands.

  // Bad
  export interface MyEventCallback {
    (event: { ... }): void;
  }
  
  export interface ABC {
    onMyEvent(callback: MyEventCallback): Disposable;
  }
  
  // Good
  export interface MyEventHandler {
    (callback: (event: { ... }) => void): Disposable;
  }
  
  export interface ABC {
    onMyEvent: MyEventHandler;
  }