babel-loader VS base-wp-theme

babel-loader

Uncaught TypeError: Object.assign is not a function I'm already using babel-loader to transpile ES6 to ES5, so all my other ES6 code is working. Yet, Object.assign() only works after I also import "babel-core/polyfill" in my codebase. I see that I can also fix this by importing babel-runtime, but I'd like to understand why Object.assign() requires more than what babel-loader performs — shouldn't babel-loader preprocess everything, including Object.assign()?

It looks like this may be an old version of webpack according to [this GitHub issue](https://github.com/babel/babel-loader/issues/798).

And babel/webpack seems to get upset at re-exporting things that don't exist at runtime (types and interfaces): https://github.com/babel/babel-loader/issues/603. So, you need to be careful to re-export your types with a different syntax, which is hard to remember when you're writing a file full of export * from 'foo'.

Apparently, this is usually a problem with Babel 7 and plugins but I've upgraded the plugins and still have this issue: https://github.com/babel/babel-loader/issues/560

There are many ways to integrate TypeScript with an existing Webpack configuration. If you use the babel-loader package to transpile JavaScript files, you can add the @babel/preset-typescript preset to generate JavaScript files and the Fork TS Checker Webpack Plugin package to run the TypeScript type checker so that the build fails if there are type errors.

In a WordPress project like this example theme, webpack avoids multiple requests, taking all our javascript and css files, and bundling all of them together in a minified file. It also increases my productivity, as, well, I don't need to manually compile and minify things.