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babel-plugin-transform-runtime

Externalise references to helpers and builtins, automatically polyfilling your code without polluting globals. (This plugin is recommended in a library/tool)

NOTE: Instance methods such as "foobar".includes("foo") will not work since that would require modification of existing builtins (Use babel-polyfill for that).

Why?

Babel uses very small helpers for common functions such as _extend. By default this will be added to every file that requires it. This duplication is sometimes unnecessary, especially when your application is spread out over multiple files.

This is where the transform-runtime plugin comes in: all of the helpers will reference the module babel-runtime to avoid duplication across your compiled output. The runtime will be compiled into your build.

Another purpose of this transformer is to create a sandboxed environment for your code. If you use babel-polyfill and the built-ins it provides such as Promise, Set and Map, those will pollute the global scope. While this might be ok for an app or a command line tool, it becomes a problem if your code is a library which you intend to publish for others to use or if you can't exactly control the environment in which your code will run.

The transformer will alias these built-ins to core-js so you can use them seamlessly without having to require the polyfill.

See the technical details section for more information on how this works and the types of transformations that occur.

Installation

NOTE - Production vs. development dependencies

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. See the examples below for more details.

Usage

Via .babelrc (Recommended)

Add the following line to your .babelrc file:

Via CLI

Via Node API

Technical details

The runtime transformer plugin does three things:

• Automatically requires babel-runtime/regenerator when you use generators/async functions. • Automatically requires babel-runtime/core-js and maps ES6 static methods and built-ins. • Removes the inline babel helpers and uses the module babel-runtime/helpers instead.

What does this actually mean though? Basically, you can use built-ins such as Promise, Set, Symbol etc as well use all the Babel features that require a polyfill seamlessly, without global pollution, making it extremely suitable for libraries.

Make sure you include babel-runtime as a dependency.

Regenerator aliasing

Whenever you use a generator function or async function:

the following is generated:

This isn't ideal as then you have to include the regenerator runtime which pollutes the global scope.

Instead what the runtime transformer does it compile that to:

This means that you can use the regenerator runtime without polluting your current environment.

core-js aliasing

Sometimes you may want to use new built-ins such as Map, Set, Promise etc. Your only way to use these is usually to include a globally polluting polyfill.

What the runtime transformer does is transform the following:

into the following:

This means is that you can seamlessly use these native built-ins and static methods without worrying about where they come from.

NOTE: Instance methods such as "foobar".includes("foo") will not work.

Helper aliasing

Usually babel will place helpers at the top of your file to do common tasks to avoid duplicating the code around in the current file. Sometimes these helpers can get a little bulky and add unnecessary duplication across files. The runtime transformer replaces all the helper calls to a module.

That means that the following code:

usually turns into:

the runtime transformer however turns this into:

Description from the npm listing.