seng-scroll-tracker/lib/ScrollTracker.d.ts

Class that keeps track of the vertical scroll position of an element.

import sengEvent from 'seng-event';
import ScrollTrackerPoint from './ScrollTrackerPoint';
import Axis from './enum/Axis';
import Side from './enum/Side';
/**
 * Class that keeps track of the vertical scroll position of an element.
 */
export default class ScrollTracker extends sengEvent {
    private element;
    private targetAxis;
    private static _DEFAULT_THROTTLE_SCROLL;
    private static _DEFAULT_THROTTLE_RESIZE;
    trackingPoints: Array<ScrollTrackerPoint>;
    viewSize: number;
    scrollSize: number;
    viewStart: number;
    viewEnd: number;
    protected lastScrollPosition: number;
    constructor(element?: HTMLElement | Window, targetAxis?: Axis);
    /**
     * Returns which axis this ScrollTracker instance is tracking.
     */
    readonly axis: Axis;
    /**
     * Returns the target element this ScrollTracker instance is tracking.
     */
    readonly targetElement: HTMLElement | Window;
    /**
     * Updates the size of the viewport of the target element.
     */
    updateSize(): void;
    /**
     * Adds a new point of which we will detect when it enters and leaves the view.
     * @param position The position of this points in pixels. This is the distance from the start
     * or end of the target element depending on the 'side' parameter, measured horizontally or
     * vertically depending on the axis of this ScrollTracker instance.
     * @param side The side from which the 'position' parameter is defined. Side.START measures the
     * position from the top or left edge and Side.END will measure the position from the bottom
     * or right edge.
     * @returns {ScrollTrackerPoint} A reference to a ScrollTrackerPoint instance that can be
     * used to bind events, remove or update the point added.
     */
    addPoint(position: number, height?: number, side?: Side): ScrollTrackerPoint;
    /**
     * Removes an existing point from this ScrollTracker. This point will be destructed and will
     * no longer throw events.
     * @param point The ScrollTrackerPoint instance to remove.
     * @returns {boolean} Boolean indicating if the point was found and removed successfully.
     */
    removePoint(point: ScrollTrackerPoint): boolean;
    /**
     * Removes all points from this ScrollTracker instance. They will be destructed and will
     * no longer throw events.
     */
    removeAllPoints(): void;
    /**
     * Initialize scroll and resize events using jQuery. Resize events will only be used when
     * the target of ScrollTracker is 'window'. If the target is not window, updateSize() has
     * to be called manually to update the view size.
     */
    protected initEvents(): void;
    /**
     * Handles events thrown by ScrollTrackerPoint instances and bubbles them up to this
     * ScrollTracker instance.
     * @param event The event thrown.
     */
    private pointEventHandler;
    protected updateScrollPosition(): void;
    /**
     * Event handler called when the target element is scrolled. Will detect the new scroll
     * position and call checkInView() on all tracking points.
     */
    protected scrollHandler: () => void;
    /**
     * Event handler called when the window resizes. Only used when the target of this ScrollTracker
     * instance is the window object.
     */
    protected windowResizeHandler: () => void;
    /**
     * Disposes this ScrollTracker and all points created on it. Removes all event handlers.
     */
    dispose(): void;
}