message: fix(bugfix): fix bug
diff: @@ -15,7 +15,6 @@ import {
  getElement,
  ease,
  offset,
  - EaseFn,
  style,
  preventDefaultExceptionFn,
  TouchEvent,
  @@ -25,7 +24,8 @@ import {
  tap,
  isUndef,
  getNow,
  - cancelAnimationFrame
  + cancelAnimationFrame,
  + EaseItem
  } from '@better-scroll/shared-utils'
  import { bubbling } from '../utils/bubbling'
  @@ -386,8 +386,9 @@ export default class Scroller {
  this.wrapperOffset = offset(this.wrapper)
  }
  - scrollBy(deltaX: number, deltaY: number, time = 0, easing = ease.bounce) {
  + scrollBy(deltaX: number, deltaY: number, time = 0, easing?: EaseItem) {
  const { x, y } = this.getCurrentPos()
  + easing = !easing ? ease.bounce : easing
  deltaX += x
  deltaY += y
  @@ -398,13 +399,14 @@ export default class Scroller {
  x: number,
  y: number,
  time = 0,
  - easing = ease.bounce,
  + easing?: EaseItem,
  extraTransform = {
  start: {},
  end: {}
  },
  isSilent?: boolean
  ) {
  + easing = !easing ? ease.bounce : easing
  const easingFn = this.options.useTransition ? easing.style : easing.fn
  const currentPos = this.getCurrentPos()
  @@ -434,10 +436,7 @@ export default class Scroller {
  time: number,
  offsetX: number | boolean,
  offsetY: number | boolean,
  - easing?: {
  - style: string
  - fn: EaseFn
  - }
  + easing?: EaseItem
  ) {
  const targetEle = getElement(el)
  const pos = offset(targetEle)
  @@ -497,7 +496,8 @@ export default class Scroller {
  this.scrollTo(pos.left, pos.top, time, easing)
  }
  - resetPosition(time = 0, easing = ease.bounce) {
  + resetPosition(time = 0, easing?: EaseItem) {
  + easing = !easing ? ease.bounce : easing
  const {
  position: x,
  inBoundary: xInBoundary
  