问题
I am getting a ReferenceError:
window is not defined when using next.js with leaflet.js .
Wondering if there's a simple solution to this problem - is using next.js overcomplicating my workflow?
for those curious with the exact code,
import React, { createRef, Component } from "react";
import L from "leaflet";
import { Map, TileLayer, Marker, Popup, DivOverlay } from "react-leaflet";
import axios from "axios";
import Header from "./Header";
export default class PDXMap extends Component {
state = {
hasLocation: false,
latlng: {
lat: 45.5127,
lng: -122.679565
},
geoJSON: null
};
mapRef = createRef();
componentDidMount() {
this.addLegend();
if (!this.state.hasLocation) {
this.mapRef.current.leafletElement.locate({
setView: true
});
}
axios
.get(
"https://opendata.arcgis.com/datasets/40151125cedd49f09d211b48bb33f081_183.geojson"
)
.then(data => {
const geoJSONData = data.data;
this.setState({ geoJSON: geoJSONData });
return L.geoJSON(this.state.geoJSON).addTo(
this.mapRef.current.leafletElement
);
});
}
handleClick = () => {
this.mapRef.current.leafletElement.locate();
};
handleLocationFound = e => {
console.log(e);
this.setState({
hasLocation: true,
latlng: e.latlng
});
};
getGeoJsonStyle = (feature, layer) => {
return {
color: "#006400",
weight: 10,
opacity: 0.5
};
};
addLegend = () => {
const map = this.mapRef.current.leafletElement;
L.Control.Watermark = L.Control.extend({
onAdd: function(map) {
var img = L.DomUtil.create("img");
img.src = "https://leafletjs.com/docs/images/logo.png";
img.style.width = "200px";
return img;
}
});
L.control.watermark = function(opts) {
return new L.Control.Watermark(opts);
};
L.control.watermark({ position: "bottomleft" }).addTo(map);
};
render() {
const marker = this.state.hasLocation ? (
<Marker position={this.state.latlng}>
<Popup>
<span>You are here</span>
</Popup>
</Marker>
) : null;
return (
<Map
className="map-element"
center={this.state.latlng}
length={4}
onClick={this.handleClick}
setView={true}
onLocationfound={this.handleLocationFound}
ref={this.mapRef}
zoom={14}
>
<TileLayer
attribution='&copy <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
/>
{marker}
</Map>
);
}
}
/**
* TODO: Add Header + Legend to map
* - Header to be styled
* - Legend to be present in header
*
*/
import React from 'react';
import PDXMap from "../components/map";
export default function SignIn() {
const classes = useStyles();
return (
<PDXMap/>
);
}
I'm happy to use any way forward - just interested in getting a functional product.
Cheers!
Update
Hey everyone,
I am still getting this error (came back to this a bit later than I had planned haha).
I am currently using this approach with useEffects,
import React, {useEffect, useState} from 'react';
function RenderCompleted() {
const [mounted, setMounted] = useState(false);
useEffect(() => {
setMounted(true)
return () => {
setMounted(false)
}
});
return mounted;
}
export default RenderCompleted;
and this is the page it is showing on
import React, { useEffect } from "react";
import Router, { useRouter } from "next/router";
import { useRef, useState } from "react";
//viz
import PDXMap from "../../components/Visualization/GIS/map";
import RenderCompleted from "../../components/utils/utils";
// import fetch from 'isomorphic-unfetch';
import { Cookies, CookiesProvider } from "react-cookie";
const cookies = new Cookies();
//containers
// Layouts
import Layout from "../../components/Layout/Layout_example";
import Chart from "../../components/Visualization/Graphs/Chart";
import Table from "../../components/Visualization/Tables/Table";
import Sidebar from "../../components/Layout/Sidebar/SidebarProperty";
export default function Bargains() {
// const [inbrowser, setBrowser] = useState(false);
const choiceRef = useRef<any>();
const [message, setMessage] = useState<any>(null);
const [productList, setProductList] = useState<any>([]);
const [searched, setSearched] = useState(false);
const router = useRouter();
let token = cookies.get("token");
// useEffect(() => {
// setBrowser(true);
// });
const isMounted = RenderCompleted();
const columns = React.useMemo(
() => [
....
],
[]
)
async function handleChoice() {
console.log("searching...", choiceRef.current?.value);
setMessage("Searching...");
var headers = {
"Content-Type": "application/x-www-form-urlencoded",
"auth-token": token,
};
fetch(
....
}
<div className="flex flex-wrap ">
{isMounted && <PDXMap/>}
<Table columns={columns as any} data={productList as any} />
</div>
</div>
</div>
</div>
</Layout>
)
}
With the same error message of
ReferenceError: window is not defined
##update two
Okay, so oddly, it does work when I browse into the site from another page, but not when i load the page itself.
Will have a think on this, but perhaps it is because the map is loading data with componentDidMount() and that is interacting weirdly?
Update
Okay I've created a more simple example based on https://github.com/rajeshdh/react-leaflet-with-nextjs
Now it is loading, but the tiles are showing incorrectly, with some tiles not loading.
This is the map component I am using to be simple,
import React, { Component, createRef } from 'react';
import { Map, TileLayer, Marker, Popup, MapControl, withLeaflet } from 'react-leaflet';
import { GeoSearchControl, OpenStreetMapProvider } from 'leaflet-geosearch';
class SearchBox extends MapControl {
constructor(props) {
super(props);
props.leaflet.map.on('geosearch/showlocation', (e) => props.updateMarker(e));
}
createLeafletElement() {
const searchEl = GeoSearchControl({
provider: new OpenStreetMapProvider(),
style: 'bar',
showMarker: true,
showPopup: false,
autoClose: true,
retainZoomLevel: false,
animateZoom: true,
keepResult: false,
searchLabel: 'search'
});
return searchEl;
}
}
export default class MyMap extends Component {
state = {
center: {
lat: 31.698956,
lng: 76.732407,
},
marker: {
lat: 31.698956,
lng: 76.732407,
},
zoom: 13,
draggable: true,
}
refmarker = createRef(this.state.marker)
toggleDraggable = () => {
this.setState({ draggable: !this.state.draggable });
}
updateMarker = (e) => {
// const marker = e.marker;
this.setState({
marker: e.marker.getLatLng(),
});
console.log(e.marker.getLatLng());
}
updatePosition = () => {
const marker = this.refmarker.current;
if (marker != null) {
this.setState({
marker: marker.leafletElement.getLatLng(),
});
}
console.log(marker.leafletElement.getLatLng());
}
render() {
const position = [this.state.center.lat, this.state.center.lng];
const markerPosition = [this.state.marker.lat, this.state.marker.lng];
const SearchBar = withLeaflet(SearchBox);
return (
<div className="map-root">
<Map center={position} zoom={this.state.zoom} style={{
height:"700px"
}}>
<TileLayer
attribution='&copy <a href="http://osm.org/copyright">OpenStreetMap</a> contributors'
url="https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
/>
<Marker
draggable={true}
onDragend={this.updatePosition}
position={markerPosition}
animate={true}
ref={this.refmarker}>
<Popup minWidth={90}>
<span onClick={this.toggleDraggable}>
{this.state.draggable ? 'DRAG MARKER' : 'MARKER FIXED'}
</span>
</Popup>
</Marker>
<SearchBar updateMarker={this.updateMarker} />
</Map>
<style jsx>{`
.map-root {
height: 100%;
}
.leaflet-container {
height: 400px !important;
width: 80%;
margin: 0 auto;
}
`}
</style>
</div>
);
}
}
And to call it I am using this,
const SimpleExample = dynamic(() => import("../../components/Visualization/GIS/map"), {
ssr: false
});
And have tried this {isMounted && }
回答1:
window is not available in SSR, you probably get this error on your SSR env.
One way to solve this is to mark when the component is loaded in the browser (by using componentDidMount method), and only then render your window required component.
class MyComp extends React.Component {
state = {
inBrowser: false,
};
componentDidMount() {
this.setState({ inBrowser: true });
}
render() {
if (!this.state.inBrowser) {
return null;
}
return <YourRegularComponent />;
}
}
This will work cause componentDidMount lifecycle method is called only in the browser.
Edit - adding the "hook" way
import { useEffect, useState } from 'react';
const MyComp = () => {
const [isBrowser, setIsBrowser] = useState(false);
useEffect(() => {
setIsBrowser(true);
}, []);
if (!isBrowser) {
return null;
}
return <YourRegularComponent />;
};
useEffect hook is an alternative for componentDidMount which runs only inside the browser.
回答2:
Answer for 2020
I also had this problem and solved it in my own project, so I thought I would share what I did.
NextJS can dynamically load libraries and restrict that event so it doesn't happen during the server side render. See the documentation for more details.
In my examples below I will use and modify example code from the documentation websites of both NextJS 10.0 and React-Leaflet 3.0.
Side note: if you use TypeScript, make sure you install @types/leaflet because otherwise you'll get compile errors on the center and attribution attributes.
To start, I split my react-leaflet code out into a separate component file like this:
import { MapContainer, Marker, Popup, TileLayer } from 'react-leaflet'
import 'leaflet/dist/leaflet.css'
const Map = () => {
return (
<MapContainer center={[51.505, -0.09]} zoom={13} scrollWheelZoom={false} style={{height: 400, width: "100%"}}>
<TileLayer
attribution='© <a href="http://osm.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>
)
}
export default Map
I called that file map.tsx and placed it in a folder called components but you might call it map.jsx if you don't use TypeScript.
Note: It is important that this code is in a separate file from where it is embedded into your page because otherwise you'll still get window undefined errors.
Also Note: don't forget to specify the style of the MapContainer component so it doesn't render as zero pixels in height/width. In the above example, I added the attribute style={{height: 400, width: "100%"}} for this purpose.
Now to use that component, take advantage of NextJS's dynamic loading like this:
import dynamic from 'next/dynamic'
function HomePage() {
const Map = dynamic(
() => import('@components/map'), // replace '@components/map' with your component's location
{ ssr: false } // This line is important. It's what prevents server-side render
)
return <Map />
}
export default HomePage
If you want the map to be replaced with something else while it's loading (probably a good practice) you should use the loading property of the dynamic function like this:
import dynamic from 'next/dynamic'
function HomePage() {
const Map = dynamic(
() => import('@components/map'), // replace '@components/map' with your component's location
{
loading: () => <p>A map is loading</p>,
ssr: false // This line is important. It's what prevents server-side render
}
)
return <Map />
}
export default HomePage
Adrian Ciura commented on the flickering which may occur as your components re-render even when nothing about the map should change. They suggest using the new React.useMemo hook to solve that problem. If you do, your code might look something like this:
import React from 'react'
import dynamic from 'next/dynamic'
function HomePage() {
const Map = React.useMemo(() => dynamic(
() => import('@components/map'), // replace '@components/map' with your component's location
{
loading: () => <p>A map is loading</p>,
ssr: false // This line is important. It's what prevents server-side render
}
), [/* list variables which should trigger a re-render here */])
return <Map />
}
export default HomePage
I hope this helps. It would be easier if react-leaflet had a test for the existence of window so it could fail gracefully, but this workaround should work until then.
回答3:
Create file loader.js, place the code below :
export const canUseDOM = !!(
typeof window !== 'undefined' &&
window.document &&
window.document.createElement
);
if (canUseDOM) {
//example how to load jquery in next.js;
window.$ = window.jQuery = require('jquery');
}
Inside any Component or Page import the file
import {canUseDOM} from "../../utils/loader";
{canUseDOM && <FontAwesomeIcon icon={['fal', 'times']} color={'#4a4a4a'}/>}
or Hook Version
import React, {useEffect, useState} from 'react';
function RenderCompleted() {
const [mounted, setMounted] = useState(false);
useEffect(() => {
setMounted(true)
return () => {
setMounted(false)
}
});
return mounted;
}
export default RenderCompleted;
Invoke Hook:
const isMounted = RenderCompleted();
{isMounted && <FontAwesomeIcon icon={['fal', 'times']} color={'#4a4a4a'}/>}
回答4:
Tiles are showing incorrectly because you miss leaflet.css. Download it from official website and just add to your project. Suddendly the map tiles will be shown correctly. Well, you won't see anything because default container size is 0,0. To fix it give a size to the container adding this on your styles.css:
.leaflet-container {
height: 450px;
width: 100%;
}
回答5:
most effective approach is suggested by @FlippingBinary I just need to argue to use little different useMemo functionality. Since useMemo is not consistent to prevent re-render when is used inside function you have to use it separately. This only works form me
vloz.tsx === Page
import React, { Suspense, lazy } from 'react';
const Vloz: React.FC = () => {
const [position, setPosition] = useState<number[] | undefined>();
const AddAd = lazy(() => import('@components/maps/AddAd'));
const MemoMap = React.useMemo(() => {
return (
<Suspense fallback={<p>Loading</p>}>
<AddAd position={position as LatLngTuple} setPosition={setPosition} />
</Suspense>
);
}, [position]);
return (
<div>
{MemoMap}
</div>
);
};
other component is normally used as other tutorials suggest.
This approach will keep Map component render til position change
回答6:
let divIcon, Map, TileLayer, Marker, Popup;
// first you must check your environment
if (process.browser) {
// then you can import
divIcon = require('leaflet').divIcon;
Map = require('react-leaflet').Map;
TileLayer = require('react-leaflet').TileLayer;
Marker = require('react-leaflet').Marker;
Popup = require('react-leaflet').Popup;
}
来源：https://stackoverflow.com/questions/57704196/leaflet-with-next-js