babel-macros π£
Enables zero-config, importable babel plugins
The problem
Currently, each babel plugin in the babel ecosystem requires that you configure it individually. This is fine for things like language features, but can be frustrating overhead for libraries that allow for compile-time code transformation as an optimization.
This solution
babel-macros defines a standard interface for libraries that want to use
compile-time code transformation without requiring the user to add a babel
plugin to their build system (other than babel-macros
, which is ideally
already in place).
Expand for more details on the motivation
For instance, many css-in-js libraries have a css tagged template string function:
const styles = css`
.red {
color: red;
}
`;
The function compiles your css into (for example) an object with generated class names for each of the classes you defined in your css:
console.log(styles); // { red: "1f-d34j8rn43y587t" }
This class name can be generated at runtime (in the browser), but this has some disadvantages:
- There is cpu usage/time overhead; the client needs to run the code to generate these classes every time the page loads
- There is code bundle size overhead; the client needs to receive a CSS parser in order to generate these class names, and shipping this makes the amount of js the client needs to parse larger.
To help solve those issues, many css-in-js libraries write their own babel plugin that generates the class names at compile-time instead of runtime:
// Before running through babel:
const styles = css`
.red {
color: red;
}
`;
// After running through babel, with the library-specific plugin:
const styles = { red: "1f-d34j8rn43y587t" };
If the css-in-js library supported babel-macros instead, then they wouldn't need their own babel plugin to compile these out; they could instead rely on babel-macros to do it for them. So if a user already had babel-macros installed and configured with babel, then they wouldn't need to change their babel configuration to get the compile-time benefits of the library. This would be most useful if the boilerplate they were using came with babel-macros out of the box, which is what we're hoping will be true for create-react-app in the future.
Although css-in-js is the most common example, there are lots of other things
you could use babel-macros
for, like:
- Compiling GraphQL fragments into objects so that the client doesn't need a GraphQL parser
- Eval-ing out code at compile time that will be baked into the runtime code, for instance to get a list of directories in the filesystem (see preval)
Installation
This module is distributed via npm which is bundled with node and
should be installed as one of your project's devDependencies
:
npm install --save-dev babel-macros
Usage
Are you trying to use babel-macros
? Go to
other/docs/user.md
.
Are you trying to make your own macros that works with babel-macros
? Go to
other/docs/author.md
.
(you should probably read the user docs too).
Inspiration
Other Solutions
Contributors
Thanks goes to these people (emoji key):
Kent C. Dodds π» π π |
Sunil Pai |
Stephen Scott π¬ π |
---|
This project follows the all-contributors specification. Contributions of any kind welcome!
LICENSE
MIT