bff6298578
* Replace lodash 'values' usage with Object.keys => .map(obj[key]) * Block scoping: refactor letReferences, outsideLetReferences as objects of type Map * Remove lodash dependency from babel-plugin-transform-block-scoping * Fixup: Add missing Object.keys call * Fixup: Update remaining property accessors * Coerce Map.values() iterator results into an array via spread operator * Fixup: Map.put -> Map.set * Fixup: undo incorrect variable de-duplication * Replace array-spread-plus-map combination with Array.from call * Extract an extendMap function as an attempt to create an optimization boundary * Experiment: cast objects to string (eliminates one Map/object difference per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map ) * Fixup: perform String cast on map keys, not values * Revert "Fixup: perform String cast on map keys, not values" This reverts commit abdd147438fa74f51ac50ef1f96bb462810cd3f2. * Revert "Experiment: cast objects to string (eliminates one Map/object difference per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map )" This reverts commit a4035c885b37bfd6e926a0362bda9dcf5b5a52c2. * Experiment: filter keys via Object.prototype.hasOwnProperty.call * Revert "Experiment: filter keys via Object.prototype.hasOwnProperty.call" This reverts commit 491c093f213c6229815b2e6dc9243245376265b0. * Migrate back from Map-based reference storage to Object-based storage; access performance appears much improved for Object property access * Revert "Migrate back from Map-based reference storage to Object-based storage; access performance appears much improved for Object property access" This reverts commit 2119acc7f0d78ced3b9ad77820b4b72e5ad67475. * Iterate over a clone of outsideRefs keys * Revert "Extract an extendMap function as an attempt to create an optimization boundary" This reverts commit 85689f2bfc180d0b5c0e674e5de7954470c7ec69. * Fixup: migrate remaining Object property access to Map.get in tdz module
Woah, what's going on here?
A monorepo, muhahahahahaha. See the monorepo design doc for reasoning.
Core Packages
| Package | Version | Dependencies |
|---|---|---|
@babel/core |
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@babel/parser |
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@babel/traverse |
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@babel/generator |
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@babel/core is the Babel compiler itself; it exposes the babel.transform method, where transformedCode = transform(src).code.
The compiler can be broken down into 3 parts:
- The parser:
@babel/parser - The transformer[s]: All the plugins/presets
- These all use
@babel/traverseto traverse through the AST
- These all use
- The generator:
@babel/generator
The flow goes like this:
input string -> @babel/parser parser -> AST -> transformer[s] -> AST -> @babel/generator -> output string
Check out the babel-handbook for more information on this.
Other
| Package | Version | Dependencies |
|---|---|---|
@babel/cli |
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@babel/types |
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@babel/polyfill |
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@babel/runtime |
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@babel/register |
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@babel/template |
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@babel/helpers |
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@babel/code-frame |
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@babel/cliis the CLI tool that runs@babel/coreand helps with outputting to a directory, a file, stdout and more (also includes@babel/nodecli). Check out the docs.@babel/typesis used to validate, build and change AST nodes.@babel/polyfillis literally a wrapper aroundcore-jsand regenerator-runtime. Check out the docs.@babel/runtimeis similar to the polyfill except that it doesn't modify the global scope and is to be used with@babel/plugin-transform-runtime(usually in library/plugin code). Check out the docs.@babel/registeris a way to automatically compile files with Babel on the fly by binding to Node.jsrequire. Check out the docs.@babel/templateis a helper function that allows constructing AST nodes from a string presentation of the code; this eliminates the tedium of using@babel/typesfor building AST nodes.@babel/helpersis a set of pre-made@babel/templatefunctions that are used in some Babel plugins.@babel/code-frameis a standalone package used to generate errors that print the source code and point to error locations.
Presets
After Babel 6, the default transforms were removed; if you don't specify any plugins/presets, Babel will just return the original source code.
The transformer[s] used in Babel are the independent pieces of code that transform specific things. For example: the es2015-arrow-functions transform specifically changes arrow functions into regular functions. A preset is simply an array of plugins that make it easier to run a whole a set of transforms without specifying each one manually.
| Package | Version | Dependencies | Description |
|---|---|---|---|
@babel/preset-env |
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automatically determines plugins and polyfills you need based on your supported environments |
You can find community maintained presets on npm
Plugins
Plugins are the heart of Babel and what make it work.
You can find community plugins on npm.
Transform Plugins
There are many kinds of plugins: ones that convert ES6/ES2015 to ES5, transform to ES3, minification, JSX, flow, experimental features, and more. Check out our website for more.
Syntax Plugins
These just enable the transform plugins to be able to parse certain features (the transform plugins already include the syntax plugins so you don't need both): @babel/plugin-syntax-x. Check out our website for more.
Helpers
These are mostly for internal use in various plugins: @babel/helper-x.