export declare class LazyAssetLoader {
    private static assets;
    /**
     *
     * Load a javascript asset to the application lazily by appending a <script> tag to <body> of index.html
     *
     * @param src the url of the script
     * @returns true if the script is new loaded, otherwise false.
     *   An ErrorObservable would be returned if the asset is failed to load.
     */
    static loadScript(src: string): Promise<boolean>;
    /**
     *
     * Load a css asset to the application lazily by appending a <link> tag to <body> of index.html
     *
     * @param href the url of the script
     * @returns true if the script is new loaded, otherwise false.
     *   An ErrorObservable would be returned if the asset is failed to load.
     */
    static loadCss(href: string): Promise<boolean>;
    /**
     * Load an asset (javascript, css, ...) to the application lazily by appending tags to <body> of index.html
     *
     * @param tagName the tag name to append
     * @param props the properties of the tag
     * @returns true if the asset is new loaded, otherwise false.
     *   An ErrorObservable would be returned if the asset is failed to load.
     */
    private static load;
}