const, let and spread (not IE11 compatible)

This library is expected to be consumed as is, however, without implicit include for babel-loader it will emit the original ES6 code to the final bundle, breaking old browsers.

Proposal:

• use ES5 inside, so it would be safe to use it
• or ship as a multi-bundle (see https://github.com/theKashey/multiple-entry-points-example)

PS: And is there any reason so spread result like return { ...memoryStatus };

[developit]

In general, the compromise the community has arrived at is to publish both ES2017 and ES5 builds. Within the next few months, bundlers like Rollup and Webpack will begin to support for Node’s new “package exports” package.json annotations, which brings a community-standardized mechanism for shipping not just CJS and ESM, but ES-current and ES5:

{
  "main": "dist/es5-cjs.js",
  "module": "dist/es5-esm.js",
  "exports": {
    ".": {
      "default": "src/index.js"
    }
  }
}

In the meantime, if the source here is strictly ES2017 (no JSX, Babel extensions, class properties, etc), a small number of bundlers are configured to look for a "jsnext:main" package.json property, and will interpret this as a signal that the package contains ES2017 code, triggering transpilation when bundling for older browsers (and using the source as-is for modern browsers).

For now, I’d recommend shipping ESM and CJS using the "module" and "main" fields, unless the package is dramatically smaller when left as ES2017. Generally I’d recommend trying a solution like microbundle, which will generate these outputs automatically, and also now includes support for compiling to modern JS.

[addyosmani]

I had wanted to circle back on whether we needed to go for multi-build depending on community feedback. I would be happy to review a PR introducing two builds if someone would like to try out an approach.