Uncaught Error: Map container is already initialized

Question

I am using React JS for making a webpage. My aim is to display a map on the front end. I am using the react-leaflet npm package for the same. However, I am getting the below error:

Error...

"Uncaught Error: Map container is already initialized.
at NewClass._initContainer (Map.js:1105:1)
at NewClass.initialize (Map.js:136:1)
at new NewClass (Class.js:22:1)
at MapContainer.js:10:1
at commitHookEffectListMount (react-dom.development.js:22969:1)
at invokePassiveEffectMountInDEV (react-dom.development.js:24948:1)
at invokeEffectsInDev (react-dom.development.js:27142:1)
at commitDoubleInvokeEffectsInDEV (react-dom.development.js:27121:1)
at flushPassiveEffectsImpl (react-dom.development.js:26865:1)
at flushPassiveEffects (react-dom.development.js:26801:1)"

Following is my code:

import React from 'react'
import { MapContainer, TileLayer, Marker, Popup } from 'react-leaflet';


const Map = () => {
return (
    <MapContainer center={[51.505, -0.09]} zoom={13}>
        <TileLayer
            attribution='&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors'
            url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
        />
        <Marker position={[51.505, -0.09]}>
            <Popup>
                A pretty CSS3 popup. <br /> Easily customizable.
            </Popup>
        </Marker>
    </MapContainer>
)
}

Answer 1

It seems an important question to me. Hence, answering here for sake of completeness. This is based on this link shared by @Satya S in the comments. React leaflet v3 won't work with reactJS v18 (as of the time of writing this response, things may change later. Use this link to verify), at least when using concurrent mode. Please try version 4 alpha of React leaflet that targets version 18 of reactJS.

Answer 2

This works for me. Hope it could help.

import React, { useEffect } from "react";
import L from "leaflet";
import "leaflet/dist/leaflet.css";
import icon from "leaflet/dist/images/marker-icon.png";
import iconShadow from "leaflet/dist/images/marker-shadow.png";

let DefaultIcon = L.icon({
iconUrl: icon,
shadowUrl: iconShadow,
});

export default function Map() {
useEffect(() => {
    var container = L.DomUtil.get("map");

    if (container != null) {
    container._leaflet_id = null;
    }
    var map = L.map("map").setView([51.505, -0.09], 13);
    L.tileLayer(
    "https://api.mapbox.com/styles/v1/{id}/tiles/{z}/{x}/{y}?access_token={accessToken}",
    {
        attribution:
        'Map data &copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors, Imagery © <a href="https://www.mapbox.com/">Mapbox</a>',
        maxZoom: 18,
        id: "mapbox/streets-v11",
        tileSize: 512,
        zoomOffset: -1,
        accessToken:
        "pk.eyJ1IjoidGFyLWhlbCIsImEiOiJjbDJnYWRieGMwMTlrM2luenIzMzZwbGJ2In0.RQRMAJqClc4qoNwROT8Umg",
    }
    ).addTo(map);
    L.Marker.prototype.options.icon = DefaultIcon;
    var marker = L.marker([51.5, -0.09]).addTo(map);
    marker.bindPopup("<b>Hello world!</b><br>I am a popup.").openPopup();
}, []);
return <div id="map" style={{ height: "100vh" }}></div>;
}

Don't forget to insert these CSS and JS to your index.html head:

<link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" integrity="sha512-hoalWLoI8r4UszCkZ5kL8vayOGVae1oxXe/2A4AO6J9+580uKHDO3JdHb7NzwwzK5xr/Fs0W40kiNHxM9vyTtQ==" crossorigin=""/>

<script src="https://unpkg.com/[email protected]/dist/leaflet.js" integrity="sha512-BB3hKbKWOc9Ez/TAwyWxNXeoV9c1v6FIeYiBieIWkpLjauysF18NzgR1MBNBXf8/KABdlkX68nAhlwcDFLGPCQ==" crossorigin=""></script>