React JS Server side issue - window not found

Here is a npm library which can handle window, document and global object for you: Global.

Then you can safely write:

import window from 'global'

const mySpecialWindowFunction = () => {
    return /msie [6-9]\b/.test(window.navigator.userAgent.toLowerCase());

If you're doing server side rendering, there's a good chance that the global window object is going to be undefined because that is only something the client will understand.

Note: Initially, when you start up your project its going to render out a complete string of your DOM (at this point it will not know about window because it is server side, but then re-render with the client-side code to which your window object will be available!

There is a workaround that I am using in this case. This is what I have for my webpack plugin:

new webpack.DefinePlugin({
  'process.env.NODE_ENV': isDevelopment ? '"development"' : '"production"',
  'process.env.BROWSER': JSON.stringify(true),
  __DEV__: isDevelopment

So I use process.env.BROWSER to my advantage because it will be defined as undefined if it is server side, and it will be true if the client side is done rendering.

Since everything just stops working when there isn't a window object on the server side we can add this:

const mySpecialWindowFunction = () => {

  /* START HACK */
  if (!process.env.BROWSER) {
    global.window = {}; // Temporarily define window for server-side
  /* END HACK */

  return /msie [6-9]\b/.test(window.navigator.userAgent.toLowerCase());

That way, your console won't scream at you and doesn't stop the server side rendering, to which you can now carry on with your glorious day! Although I have to admit that this is a bit Hacky, but it gets the job done because all we want to do is let the server side render out the initial DOM string and then let the client-side take over.

Also Note: Don't worry about setting window as an empty object, it will be back to normal once the client-side finishes rendering.