The bootstrap 4.1 download from https://github.com/twbs/bootstrap/tree/v4.1.0 includes too many files/folders that we do not need: _data, _includes, _layouts, assests, dist, docs, nuget...

We just keep

• folder "js/src" (remove js/dist, js/tests)
• folder "scss"
• build/rollup.config.js & build/postcss.config.js
• package.json find and remove all scripts name includes "docs", "lint", "test"... and remove all useless (for us) dependencies, change "index.js" to "index-app.js" and "bootstrap.scss" to "bootstrap-app.scss" and config the generated js to outside of the "js" folder, moving all to "dist" folder.
• .babelrc.js

You can download the final from this git. As they release new version, just copy 2 folders "js/src" & "sass", of course in case they do not change the build process.

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After download bootstrap 4 source, we run install

$ npm install

and get "python" error and stuck from this. The reason is that: bootstrap use note-sass to compile sass files, on windows this package require node-gyp prerequisites.

https://github.com/nodejs/node-gyp#on-windows

We have to install windows-build-tools from CMD/PowerShell running as Administrator

$ npm install --global --production windows-build-tools

This will automatically install [Visual C++ Build Tools] and Python 2.7 (exactly version 2.7, v3.x.x is not supported) [Python version 2.7] . The installation takes place about 10 minutes or more. After finished, you can find Python 2.7 installed in folder C:\Users\USER-NAME\.windows-build-tools\python27

That's fine, now take back to the working space, set evn "python" to the file "python.exe"

$ npm config set python C:\Users\\*USER-NAME*\\.windows-build-tools\python27\python.exe

Now you can start "npm install" and get the results.

===

When everything's okay, just run

$ npm run dist the results will be in "dist" folder.