Following on from this question I have set up my Webpack 4 config to handle babel-loader like this
{
module : {
rules : [{
test : /\.js$/,
// Some module should not be transpiled by Babel
// See https://github.com/zloirock/core-js/issues/743#issuecomment-572074215
exclude: ['/node_modules/', /\bcore-js\b/, /\bwebpack\/buildin\b/, /@babel\/runtime-corejs3/],
loader : "babel-loader",
options : {
babelrc : false,
// Fixes "TypeError: __webpack_require__(...) is not a function"
// https://github.com/webpack/webpack/issues/9379#issuecomment-509628205
// https://babeljs.io/docs/en/options#sourcetype
sourceType : "unambiguous",
presets : [
["@babel/preset-env", {
// Webpack supports ES Modules out of the box and therefore doesn’t require
// import/export to be transpiled resulting in smaller builds, and better tree
// shaking. See https://webpack.js.org/guides/tree-shaking/#conclusion
modules : false,
// Adds specific imports for polyfills when they are used in each file.
// Take advantage of the fact that a bundler will load the polyfill only once.
useBuiltIns : "usage",
corejs : {
version : "3",
proposals : true
}
}]
]
}
}
}
}
When I run this in the browser I get this error which I do not understand:
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
TypeError: Cannot convert undefined or null to object
What is the fix for this? Following this question I have searched everywhere for code starting import 'core-js but cannot see it anywhere so have reached a dead end.