/// import * as React from 'react'; export interface BackTopProps { visibilityHeight?: number; onClick?: React.MouseEventHandler; target?: () => HTMLElement | Window; prefixCls?: string; className?: string; style?: React.CSSProperties; } export default class BackTop extends React.Component { static defaultProps: { visibilityHeight: number; }; scrollEvent: any; constructor(props: BackTopProps); getCurrentScrollTop: () => number; scrollToTop: (e: React.MouseEvent) => void; setScrollTop(value: number): void; handleScroll: () => void; componentDidMount(): void; componentWillUnmount(): void; render(): JSX.Element; }