Pre-build Unused Code Eliminator for JavaScript
npm install prelimPrelim is an unused code removal (dead code elimination) tool for javascript.
Unlike other tools in this space, such as babel-minify or terserjs, prelim is
focused on the "pre-build" use case: it's meant to be used outside of a build
process to find and remove no-longer-used code so that humans can better read
and understand their code.
You can run prelim directly on your source folder, like:
``sh`
npx prelim src/
You can also use prelim in conjunction with other tools, such as a codemod or
find-replace to remove a no-longer-used feature flag.
You can also use prelim as a babel plugin if you would like (although at the
moment prelim provides more benefit when run outside of a build process, it
can produce some savings that terserjs may not be able to identify as unused).
Installation:
`sh`
npm install --save-dev prelim
Useage: as a cli:
`sh`
npx prelim src/directory/
Or as a babel plugin:
`javascriptloose:
module.exports = {
/ ... /
plugins: [
// enables not-strictly safe optimizations, and is recommendedfalse
// for code that does not have getters/proxies with side-effects.
// The default is (equivalent to --strict in the cli)``
['prelim', { loose: true }],
],
};
Prelim supports a few different types of optimizations:
Prelim can find and delete unused variables whose initializations appear to be
free of side effects.
Prelim can find and delete unused properties in object literal variables whose
values appear to be free of side effects.
Prelim can find and replace if statements and conditional operator expressions
where only one branch is taken because the condition always evaluates to a truthy
or falsy value.
Prelim can simplify if-conditions and other boolean expressions where parts of
the expression always evaluate to truthy or falsy values.
Please report bugs or issues you run into with [github issues][issues].
[issues]: https://github.com/ariabuckles/prelim/issues
Please see CONTRIBUTING.md for background for contributing.
Prelim is MIT licensed.