React create app hot reload is not always working

问题:

I created a react application using create-react-app boilerplate, which seems to be very popular, hot reload some times updates when any of the files changes and some times not, seems like there is a minimum duration or something like that, I'm using Ubuntu, node version 7.0, the script in package.json is npm:'react-script start' what I am missing ?

回答1:

When npm start doesn’t detect changes, below are the common troubleshooting steps provided in the create-react-app documentation - link.

While an app is running with npm start and updating code in the editor should possibly refresh the borswer with the updated code. If this doesn’t happen, try one of the following workarounds:

1. If the project files are directly synced to your local system from a cloud storage like Dropbox or Google Drive and your trying to run the app in them directly, try moving it out.
2. Due to Webpack bug, you may need to restart the watcher. If the watcher doesn’t detect the index.js and you’re referencing it by the folder name.
3. Safe write feature in editors like Vim and IntelliJ currently breaks the watcher. You will need to disable it.
4. Due to Webpack watcher bug, projects with path contains parentheses causes issue, try moving the project to a path without them. .
5. To allow more watchers in Linux and macOS, you might need to tweak system settings.
6. If the project runs inside a virtual machine such as (a Vagrant provisioned) VirtualBox, create an .env file in your project directory if it doesn’t exist, and add CHOKIDAR_USEPOLLING=true to it. This ensures that the next time you run npm start, the watcher uses the polling mode, as necessary inside a VM.
7. Could try increasing max_users_watches- link

More references:

• Issue Tracker 1
• Toubleshooting webpack
• Issue Tracker 2 - Webpack polling

回答2:

Try these:

• Turn off safe write in your IDE
• Increase max_user_watches
• Your path should not have parentheses

as last resort try to use this as your env variable: CHOKIDAR_USEPOLLING=true npm start

Sources: https://github.com/facebookincubator/create-react-app/issues/659 https://github.com/facebookincubator/create-react-app/issues/1049#issuecomment-261731734

回答3:

In unbuntu, i basically kill all the process running on port (for react app default is :3000).

List all the process running on port 3000.

lsof -i :3000

This command will show something like this.

COMMAND   PID USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
node     7429 yipl   19u  IPv4 1081760      0t0  TCP localhost:3000->localhost:35762 (ESTABLISHED)
chrome  26448 yipl  177u  IPv4 1080082      0t0  TCP localhost:35762->localhost:3000 (ESTABLISHED)

Now kill the process by PID.

kill -9 7429
kill -9 26488

Start your react app again.

回答4:

Apparently hot module reloading only works out-of-the-box if you eject your app.

But if you haven't ejected your app, then you can follow these instructions to get it working.

Find the ReactDOM.render(...) at the top of your app, and add these lines below it:

ReactDOM.render(...);

if (module.hot) {
  module.hot.accept('./App', () => {
    // --- Copy-paste your usual ReactDOM.render(...) call here: --- //
    ReactDOM.render(...);
  });
}

The instructions linked above also show how to hot reload things outside of the component tree, such as redux reducers.

回答5:

One additional case I just experience is when using multiple version of nodejs with NVM in parallel. Basically, I have two terminal windows, one run node 10.x, other on node 9.x, and Webpack watcher stops seeing change.

The solution is to bring both to the same node version

回答6:

I was able to make this work using:

sudo npm start