每个 event 都有一个event.bubbles属性，可以知道它可否冒泡。
| Event Type | Bubbling phase |
|---|---|
| abort | ✗ |
| beforeinput | ✔ |
| blur | ✗ |
| click | ✔ |
| compositionstart | ✔ |
| compositionupdate | ✔ |
| compositionend | ✔ |
| dblclick | ✔ |
| error | ✗ |
| focus | ✗ |
| focusin | ✔ |
| focusout | ✔ |
| input | ✔ |
| keydown | ✔ |
| keyup | ✔ |
| load | ✗ |
| mousedown | ✔ |
| mouseenter | ✗ |
| mouseleave | ✗ |
| mousemove | ✔ |
| mouseout | ✔ |
| mouseover | ✔ |
| mouseup | ✔ |
| resize | ✗ |
| scroll | ✔ |
| select | ✔ |
| unload | ✗ |
| wheel | ✔ |