DOM Event

// if (e.pageX || pageY) -> MouseEvent
// if (e.locale || location) -> KeyboardEvent

interface UIEvent {
  /**
   * 当前点击数
   * click,dbclick - n
   * mousedown, mouseup - detail+1
   */
  readonly detail: number;
  /**
   * =document.defaultView
   */
  readonly view: Window | null;
  /**
   * keyCode 的 charCode
   *
   * @deprecated
   */
  readonly which: number;

  /**
   * 设备操作能力
   */
  sourceCapabilities: InputDeviceCapabilities | null;
}

// Mouse 和 Keyboard 都有的属性
interface CommonEvent extends UIEvent {
  /**
   * Windows alt, macOS option
   */
  readonly altKey: boolean;
  readonly ctrlKey: boolean;
  /**
   * Wdinwos ⊞ Win, macOS ⌘ Command
   */
  readonly metaKey: boolean;
  readonly shiftKey: boolean;
}

interface KeyboardEvent extends CommonEvent {
  /**
   * 判断按键输入位置 - 标准、左、右、数字键盘、移动设备、摇杆
   */
  readonly location: number;
  readonly repeat: boolean;
  readonly code: string;
  /**
   * 在 compositionstart 和 compositionend 之间 - 输入法正在输入的过程
   */
  readonly isComposing: boolean;
  readonly key: string;
  /**
   * @deprecated
   */
  readonly charCode: number;
  /**
   * @deprecated
   */
  readonly keyCode: number;
}
interface MouseEvent extends CommonEvent {
  /**
   * 0 - main,left, 1 - auxiliary,middle, 2 - secondary,right
   * 3 - back, 4 - forward
   */
  readonly button: number;
  /**
   * button 组合，使用 bit mask
   */
  readonly buttons: number;

  readonly clientX: number;
  readonly clientY: number;
  /**
   * 非标准属性，但所有浏览器都支持
   * 值会考虑 scrolling
   */
  readonly layerX: number;
  readonly layerY: number;

  readonly movementX: number;
  readonly movementY: number;
  readonly offsetX: number;
  readonly offsetY: number;
  readonly pageX: number;
  readonly pageY: number;
  readonly screenX: number;
  readonly screenY: number;
  readonly x: number;
  readonly y: number;

  // secondary target
  // 用于 MouseEvent - 与 target 对应
  // 事件: mouseenter, mouseleave, mouseout, mouseover, dragenter, dragleave
  // mouseenter - 进入 target 退出 relatedTarget
  // mouseleave - 退出 target 进入 relatedTarget
  relatedTarget: EventTarget | null;
}

interface SyntheticEvent<E = object, C = any, T = any> {
  nativeEvent: E;
  currentTarget: C;
  target: T;
  bubbles: boolean;
  cancelable: boolean;
  defaultPrevented: boolean;
  eventPhase: number;
  isTrusted: boolean;
  preventDefault(): void;
  //
  isDefaultPrevented(): boolean;
  stopPropagation(): void;
  isPropagationStopped(): boolean;
  // ReactDOM v17 现在无效
  persist(): void;
  timeStamp: number;
  type: string;
}