DefinitelyTyped/types/next/router.d.ts

import * as React from 'react';

export interface EventChangeOptions {
    shallow?: boolean;
    [key: string]: any;
}

export type RouterCallback = () => void;
export interface SingletonRouter {
    readyCallbacks: RouterCallback[];
    ready(cb: RouterCallback): void;

    // router properties
    readonly components: { [key: string]: { Component: React.ComponentType<any>, err: any } };
    readonly pathname: string;
    readonly route: string;
    readonly asPath?: string;
    readonly query?: { [key: string]: any };

    // router methods
    reload(route: string): Promise<void>;
    back(): void;
    push(url: string, as?: string, options?: EventChangeOptions): Promise<boolean>;
    replace(url: string, as?: string, options?: EventChangeOptions): Promise<boolean>;
    prefetch(url: string): Promise<React.ComponentType<any>>;

    // router events
    onAppUpdated?(nextRoute: string): void;
    onRouteChangeStart?(url: string): void;
    onBeforeHistoryChange?(as: string): void;
    onRouteChangeComplete?(url: string): void;
    onRouteChangeError?(error: any, url: string): void;
}

export const Singleton: SingletonRouter;
export default Singleton;