Transform leaflet marker plugin into Typescript format

I recently discovered a leaflet extension that conceals map markers if they fall outside the boundaries of the current view map.

import L from 'leaflet';

L.Marker.MyMarker= L.Marker.extend({}).addInitHook(function (this: ILazyMarker) {
    this.on(
        'add',
        function (this: ILazyMarker) {
            this._updateIconVisibility = function (this: ILazyMarker) {
                var map = this._map,
                    isVisible = map.getBounds().contains(this.getLatLng()),
                    wasVisible = this._wasVisible,
                    icon = this._icon,
                    iconParent = this._iconParent,
                    shadow = this._shadow,
                    shadowParent = this._shadowParent;

                // keep track of parent of icon
                if (!iconParent) {
                    iconParent = this._iconParent = icon.parentNode;
                }
                if (shadow && !shadowParent) {
                    shadowParent = this._shadowParent = shadow.parentNode;
                }

                // remove or add to DOM based on visibility change
                if (iconParent != null && isVisible != wasVisible) {
                    if (isVisible) {
                        iconParent.appendChild(icon);
                        if (shadowParent != null && shadow) {
                            shadowParent.appendChild(shadow);
                        }
                    } else {
                        iconParent.removeChild(icon);
                        if (shadowParent != null && shadow) {
                            shadowParent.removeChild(shadow);
                        }
                    }

                    this._wasVisible = isVisible;
                }
            };

            // update icon visibility on map size change
            this._map.on('resize moveend zoomend', this._updateIconVisibility, this);
            this._updateIconVisibility();
        },
        this,
    );
});

The functionality works flawlessly, but I prefer using a Typescript class for uniformity across my project. Below is my attempt at converting it:

import L from 'leaflet';

export default class MyMarker extends L.Marker {
    _wasVisible!: boolean;
    _icon!: any;
    _shadowParent!: any;
    _iconParent!: any;

    constructor(latlng: L.LatLngExpression, options?: L.MarkerOptions) {
        super(latlng, options);
    }

    onAdd(): this {
        this._map.on('resize moveend zoomend', this._updateIconVisibility, this);
        this._updateIconVisibility();
        return this;
    }

    _updateIconVisibility() {
        var map = this._map,
            isVisible = map.getBounds().contains(this.getLatLng()),
            wasVisible = this._wasVisible,
            icon = this._icon,
            iconParent = this._iconParent,
            shadow = this._shadow,
            shadowParent = this._shadowParent;

        // remember parent of icon
        if (!iconParent) {
            iconParent = this._iconParent = icon.parentNode;
        }
        if (shadow && !shadowParent) {
            shadowParent = this._shadowParent = shadow.parentNode;
        }

        // add/remove from DOM on change
        if (iconParent != null && isVisible != wasVisible) {
            if (isVisible) {
                iconParent.appendChild(icon);
                if (shadowParent != null && shadow) {
                    shadowParent.appendChild(shadow);
                }
            } else {
                iconParent.removeChild(icon);
                if (shadowParent != null && shadow) {
                    shadowParent.removeChild(shadow);
                }
            }

            this._wasVisible = isVisible;
        }
    }
}

However, when trying to use this marker class, I encounter an error for each marker added and the map fails to render:

TypeError: Cannot read property 'parentNode' of undefined
    at MyMarker._updateIconVisibility (leaflet-my-marker.ts:78)
    at MyMarker.onAdd (leaflet-my-marker.ts:63)
    at MyMarker._layerAdd (leaflet-src.js:6567)
    at NewClass.whenReady (leaflet-src.js:4428)
    at NewClass.addLayer (leaflet-src.js:6629)
    at NewClass.addLayer (leaflet-src.js:6780)
    at VueComponent.addLayer (LLayerGroup.js:164)
    at VueComponent.FirecamMarker.mounted (MyMarker.vue?6277:99)
    at invokeWithErrorHandling (vue.runtime.esm.js:1854)
    at callHook (vue.runtime.esm.js:4219)
typescriptvue.jsleaflet

Answer №1

According to the "Law of Code Dilemma": No matter how much time you spend troubleshooting a coding issue, the solution will only reveal itself once you seek help on an online forum.

I dedicated several days to dissecting this problem... only to find the answer miraculously shortly after seeking assistance on an online platform. It turns out, I needed to invoke the super's onAdd method within my own onAdd method, as demonstrated below:

onAdd(): this {
    super.onAdd(this._map);
    this._map.on('resize moveend zoomend', this._updateIconVisibility, this);
    this._updateIconVisibility();
    return this;
}

The reason for this oversight was that the original code referenced `addInitHook()` instead of `setInitHook()`, hence the confusion.

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