README.md

Corejs Bundle Size Regression Repro

Summary

In this repo, we simulate 3 scenarios and the code to simulate them are each in their respective folders.

Scenario	Description
babel-runtime	Compile JS using standard configuration for babel-runtime. Thus dependencies resolve to @babel/runtime package
babel-runtime-corejs2	Compile JS using corejs: 2 configuration for babel-runtime. Thus dependencies resolve to @babel/runtime-corejs2 package
babel-runtime-corejs3	Compile JS using corejs: 3 configuration for babel-runtime. Thus dependencies resolve to @babel/runtime-corejs3 package

Setup

Install dependencies and build assets

yarn install
yarn build

Inspect bundle sizes

Run the following commands (after building) to inspect bundle size after minification.

ls -lh out/ | grep min

Output (Notice corejs 2 and 3 are significantly larger than the standard babel-runtime usage):

-rw-r--r--  1 gtaveras  320754065    14K Apr 12 11:23 babel-runtime-corejs2.min.js
-rw-r--r--  1 gtaveras  320754065    22K Apr 12 11:23 babel-runtime-corejs3.min.js
-rw-r--r--  1 gtaveras  320754065   2.0K Apr 12 11:23 babel-runtime.min.js