CODEWITHSUNDEEP
javascriptreactjsexpresswebpackwebpack-dev-server
Pavel Perevezencev
Pavel Perevezencev

Reputation: 2978

Text content did not match. Warning in React 16

I trying to build ReactJs application with server side rendering My entry points for client and server:

client.jsx

const store = createStore(window.__INITIAL_STATE__);

hydrate(
  <Provider store={store}>
    <BrowserRouter>{renderRoutes(routes)}</BrowserRouter>
  </Provider>,
  document.querySelector('#root')
);

server.jsx

const app = express();

if (isDev) {
  const webpack = require('webpack');
  const webpackDevMiddleware = require('webpack-dev-middleware');
  const config = require('../../webpack.config.js');
  const compiler = webpack(config);

  app.use(express.static('/public'));
  app.use(
    webpackDevMiddleware(compiler, {
      publicPath: config.output.publicPath,
      stats: 'errors-only',
    })
  );
}

app.get('*', (req, res) => {
  const helmet = Helmet.renderStatic();
  const htmlAttrs = helmet.htmlAttributes.toComponent();
  const bodyAttrs = helmet.bodyAttributes.toComponent();

  const context = {};
  const data = {};

  res.set('content-type', 'text/html');

  res.send(
    '<!DOCTYPE html>' +
      renderToString(
        <html {...htmlAttrs}>
          <head>
            {helmet.title.toComponent()}
            {helmet.meta.toComponent()}
            {helmet.link.toComponent()}
          </head>
          <body {...bodyAttrs}>
            <div id="root">
              <StaticRouter location={req.url} context={context}>
                {renderRoutes(routes)}
              </StaticRouter>
            </div>
            <script
              dangerouslySetInnerHTML={{
                __html: `window.__INITIAL_STATE__ = ${JSON.stringify(data)}`,
              }}
            />
            <script src="/public/vendor.js" />
            <script src="/public/app.js" />
          </body>
        </html>
      )
  );
});

And component:

home.jsx

import React, { Component } from 'react';

class Home extends Component {
  render() {
    return <div>home</div>;
  }
}

export default Home;

When I change in my component Home and refresh browser page I get this error:

Warning: Text content did not match. Server: "home" Client: "home1"

Its ok because server render old version of my code. How to reload the code on the server so that the client and server versions are equal?

Upvotes: 26

Views: 39617

Answers (3)

meotimdihia
meotimdihia

Reputation: 4299

No one said about but Cloudflare replaced double spaces with a space when you enable Auto Minify (HTML) in optimization. And this error will happen.

Upvotes: 1

Cyral
Cyral

Reputation: 14153

For those discovering this error because your client and server purposefully render different content (like the server rendering a dark theme which gets replaced with the user preference on load), use suppressHydrationWarning to suppress the error.

For example:

<div suppressHydrationWarning>Ignore this</div>

Upvotes: 33

mpospelov
mpospelov

Reputation: 1549

The problem here is that your server-side application does not reflect code changes. To do that you have to configure your express app as a webpack entry.

Briefly, you need 2 webpack configurations one for server and another for client code. The server one will look something like this

module.exports = {
  entry: {
    server: './server.js',
  },
  output: {
    path: path.join(__dirname, 'dist'),
    publicPath: '/',
    filename: '[name].js'
  },
  target: 'node',
  node: {
    // Need this when working with express, otherwise the build fails
    __dirname: false,   // if you don't put this is, __dirname
    __filename: false,  // and __filename return blank or /
  },
  externals: [nodeExternals()], // Need this to avoid error when working with Express
  module: {
    rules: [
      {
        // Transpiles ES6-8 into ES5
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: "babel-loader"
        }
      },
      {
        // Loads the javacript into html template provided.
        // Entry point is set below in HtmlWebPackPlugin in Plugins 
        test: /\.html$/,
        use: [{loader: "html-loader"}]
      }
    ]
  },
  plugins: [
    new HtmlWebPackPlugin({
      template: "./index.html",
      filename: "./index.html",
      excludeChunks: [ 'server' ]
    })
  ]
}

Here is a nice article explaining how to do that in details

Upvotes: 3

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