export interface Callback {
    (): void;
}
/**
 * Handles loading a resource DOM element and listening for when it's
 * finished or failed to load.
 *
 * This is designed to handle race conditions whereby a resource
 * added but not yet fully loaded. Event handlers can be registered
 * even after a resource has loaded with event handlers being fired.
 */
export declare class ResourceElement {
    #private;
    ready: boolean;
    failed: boolean;
    constructor(resource: HTMLScriptElement | HTMLLinkElement);
    /**
     * A callback made by the resource DOM element for
     * when the resource has loaded successfully.
     */
    private onload;
    /**
     * A callback made by the resource DOM element for
     * when the resource fails to load.
     */
    private onerror;
    /**
     * Add event listeners for when a resource has loaded or failed to load.
     *
     * @param onLoad A callback for when the resource has loaded successfully.
     * @param onError A callback for when the resource has failed to load.
     */
    addListeners(onLoad: Callback, onError: Callback): void;
    /**
     * Removes load and error event listeners.
     *
     * @param onLoad A callback for when the resource has loaded successfully.
     * @param onError A callback for when the resource has failed to load.
     */
    removeListeners(onLoad: Callback, onError: Callback): void;
    /**
     * Checks whether any callback handlers need to be invoked.
     */
    private checkLoaded;
}