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I am doing Server Side Rendering for the first time with React and Redux and seeming to be having a little difficulty. I am getting the warning:
Warning: Did not expect server HTML to contain a <li> in <ul>.
I have looked this up and it means that there is a html tree mismatch. I am not sure how that is. Is there an obvious way to fix it? Here is the code I have that is throwing the warning.
import React, { Component } from 'react';
import { connect } from 'react-redux';
import actions from '../actions';
class UsersList extends Component {
componentDidMount() {
if (this.props.users.length > 0) {
return;
}
this.props.fetchUsers();
}
render() {
const { users } = this.props;
return (
<div>
<ul>
{users.map(user => {
return <li key={user.id}>{user.name}</li>;
})}
</ul>
</div>
);
}
}
const stateToProps = state => {
return {
users: state.users
};
};
const dispatchToProps = dispatch => {
return {
fetchUsers: () => dispatch(actions.fetchUsers())
};
};
const loadData = store => {
return store.dispatch(actions.fetchUsers());
};
export { loadData };
export default connect(stateToProps, dispatchToProps)(UsersList);
Here is the client.js:
// Startup point for the client side application
import 'babel-polyfill';
import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter } from 'react-router-dom';
import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import { Provider } from 'react-redux';
import { renderRoutes } from 'react-router-config';
import Routes from './Routes';
import reducers from './reducers';
const store = createStore(reducers, {}, applyMiddleware(thunk));
ReactDOM.hydrate(
<Provider store={store}>
<BrowserRouter>
<div>{renderRoutes(Routes)}</div>
</BrowserRouter>
</Provider>,
document.querySelector('#root')
);
428
The problem was that since the server had rendered the list of users already, it had a ul with lis. But when the client loaded there was no initial data so there was only an ul and no lis to accompany it.
To fix this problem, which I think not many will have because you need to do this anyway in server side rendering is to pass some initial state into the createStore redux function:
You will need to do this in two places. In the html on your server side and in your entry point on the client side.
Short example could be:
<html>
<head></head>
<body>
<div id="root">${content}</div>
<script>
window.INITIAL_STATE = ${serialize(store.getState())}
</script>
<script src="bundle.js"></script>
</body>
</html>
As you can see we have to set the initial state to the store that you created on your server side.
On your client side:
// Startup point for the client side application
import 'babel-polyfill';
import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter } from 'react-router-dom';
import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import { Provider } from 'react-redux';
import { renderRoutes } from 'react-router-config';
import Routes from './Routes';
import reducers from './reducers';
const store = createStore(reducers, window.INITIAL_STATE, applyMiddleware(thunk));
ReactDOM.hydrate(
<Provider store={store}>
<BrowserRouter>
<div>{renderRoutes(Routes)}</div>
</BrowserRouter>
</Provider>,
document.querySelector('#root')
);
Now you have access to this global variable window.INITIAL_STATE and you just pass that through into the second argument of createStore which is the initial state.
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