Some libraries (e.g. React) don't want to rely on the user polyfilling
Object.assign and therefore use sindresorhus's ponyfill
although all modern browser and nodejs versions support it flawlessly.
While not a noticeable in size for most apps it is still half a kb minified and gziped that isn't necessary. Luckily most bundlers allow for modules to be replaced at build time with another one.
When using webpack just add the following lines to your config:
const webpack = ;// ...plugins:/^object-assign/"object-assign-native"// ...