babel vs babel-core vs babel-runtime

Question

My node webpack project uses three babel libraries. What's the difference between these and how are they being used?

"dependencies": {
  "babel-runtime": "^5.8.24"
}

"dev-dependencies": {
  "babel": "^5.8.23",
  "babel-core": "^5.8.23"
}

Answer 1

The Six Things You Need To Know About Babel 6 explained it quite well, to quote

The babel npm package no longer exists. Instead, Babel has been split into multiple packages:

babel-cli, which contains the babel command line interface babel-core, which contains the Node API and require hook babel-polyfill, which when required, sets you up with a full ES2015-ish environment To avoid accidental conflicts, make sure to remove any previous Babel packages like babel, babel-core, etc. from your package.json, and then npm uninstall them.

Answer 2

TL;DR The things to compare here are:

1. babel (use for 5.x.x) vs babel-cli+babel-core (pick one for 6.x.x)
2. babel-polyfill (use for non-libraries) vs babel-runtime+babel-plugin-transform-runtime (use for libraries)

From https://babeljs.io/blog/2015/10/31/setting-up-babel-6:

The babel package is no more. Previously, it was the entire compiler and all the transforms plus a bunch of CLI tools, but this lead to unnecessarily large downloads and was a bit confusing. Now we’ve split it up into two separate packages: babel-cli and babel-core.

npm install --global babel-cli

or

npm install --save-dev babel-core

If you want to use Babel from the CLI you can install babel-cli or if you want to use the Node API you can install babel-core.

babel-runtime just allows polyfills that don't pollute the global space, unlike babel-polyfill which pollutes your global space. From http://babeljs.io/docs/plugins/transform-runtime/:

[babel-runtime] automatically polyfills your code without polluting globals. (This plugin is recommended in a library/tool)

If you use babel-runtime, you should also

npm install --save-dev babel-plugin-transform-runtime

In most cases, you should install babel-plugin-transform-runtime as a development dependency (with --save-dev) and babel-runtime as a production dependency (with --save).

The transformation plugin is typically used only in development, but the runtime itself will be depended on by your deployed/published code.

Also, babel-runtime+babel-plugin-transform-runtime and babel-polyfill are generally mutually exclusive--meaning you should only use one or the other. From a comment here http://jamesknelson.com/the-six-things-you-need-to-know-about-babel-6/:

You should be using either babel-polyfill or babel-runtime. They are mutually exclusive—unless of course you know what you are doing. But they are essentially the same thing. These are just helpers. babel-polyfill achieves the same goal by mutating globals whereas babel-runtime does so modularly. Unless you are developing a library, I’d recommend you use the polyfill.

Answer 3

babel-core is the API. For v5 the babel package is the CLI and depends on babel-core. For v6, the babel-cli package is the CLI (the CLI bin command is still babel though) and the babel package doesn't do anything. babel-runtime I guess is just the runtime (polyfill and helpers) to support code that's already been transformed.