React SDK: Error building app with webpack "Entrypoint undefined = ng/index.html"

Issue

React App failed to build using Webpack after installing React SDK:

1 asset
Entrypoint undefined = ng/admin_index.html
[./node_modules/html-webpack-plugin/lib/loader.js!./admin_index.html] 1.89 KiB {0} [built]
[./node_modules/html-webpack-plugin/node_modules/lodash/lodash.js] 527 KiB {0} [built]
[./node_modules/webpack/buildin/global.js] (webpack)/buildin/global.js 472 bytes {0} [built]
[./node_modules/webpack/buildin/module.js] (webpack)/buildin/module.js 497 bytes {0} [built]
Child html-webpack-plugin for "ng\index.html":
1 asset
Entrypoint undefined = ng/index.html
[./node_modules/html-webpack-plugin/lib/loader.js!./index.html] 1.91 KiB {0} [built]
[./node_modules/html-webpack-plugin/node_modules/lodash/lodash.js] 527 KiB {0} [built]
[./node_modules/webpack/buildin/global.js] (webpack)/buildin/global.js 472 bytes {0} [built]
[./node_modules/webpack/buildin/module.js] (webpack)/buildin/module.js 497 bytes {0} [built]
i ?wdm?: Failed to compile.

Root Cause

Webpack is trying to build the React SDK library into the server side, which will cause errors since React SDK is designed to run only on browser side. 

Answer

To resolve the issue, open webpack.config.js file, locate the resolve section, make sure the mainFields entry contain browser similar to the below example:

resolve: {
      extensions: ['.js', '.json', '.ts', '.tsx'],
      mainFields: ['browser', 'main', 'module']
    },