Registry / serialization / babel-dead-code-elimination

babel-dead-code-elimination

library1.0.12jsnpmunverified

A library providing composable primitives for dead code elimination in Babel AST, version 1.0.12. It is not a Babel plugin but a set of utilities (deadCodeElimination, findReferencedIdentifiers) to integrate into custom transforms. Released as a stable package with frequent patches, it differs from full-featured plugins by offering fine-grained control and working directly with the AST. Main use cases: removing unused variables, handling side-effects carefully via referenced identifier tracking, and preserving runtime behavior (e.g., object rest patterns). Ships TypeScript types.

serialization

npm install babel-dead-code-elimination

github ↗package ↗

INSTALL

IMPORT

SIG · BABEL-DEAD-CODE-EL

babel-dead-code-elimination

serializationjavascriptv1.0.12

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

deadCodeElimination

✓ import { deadCodeElimination } from 'babel-dead-code-elimination'

✗ import deadCodeElimination from 'babel-dead-code-elimination'

Named export, not default. This is ESM. For CommonJS, use const { deadCodeElimination } = require('babel-dead-code-elimination').

findReferencedIdentifiers

✓ import { findReferencedIdentifiers } from 'babel-dead-code-elimination'

✗ const findReferencedIdentifiers = require('babel-dead-code-elimination').findReferencedIdentifiers

Also a named export. CommonJS require destructuring works but named import is preferred for ESM.

types

✓ import type { ... } from 'babel-dead-code-elimination'

The package ships TypeScript types but does not export them directly (e.g., no 'types' export). You can import the functions as usual and types are inferred.

Parses a module, eliminates unreferenced variable 'b', then regenerates code. Shows basic usage.

import { parse } from '@babel/parser' import generate from '@babel/generator' import { deadCodeElimination } from 'babel-dead-code-elimination' const source = ` const a = 1 const b = 2 console.log(a) ` const ast = parse(source, { sourceType: 'module' }) deadCodeElimination(ast) const result = generate(ast).code console.log(result) // Expected output: "const a = 1;\nconsole.log(a);"

Debug

Known issues

gotchadeadCodeElimination will remove variables even if they have side-effects in their initializer (e.g., const x = sideEffect()) unless you pass a set of referenced identifiers.

fix

Use findReferencedIdentifiers before transforms and pass the set as second argument to deadCodeElimination to preserve existing references.

affects: >=1.0.0

deprecatedIn v1.0.5 and earlier, function expressions were incorrectly eliminated. This was fixed in v1.0.4 and v1.0.5.

fix

Upgrade to >=1.0.5 to avoid eliminating function expressions.

affects: <1.0.4

breakingIn v1.0.9, object pattern rest elements behave differently: unused variables before rest are preserved to avoid changing rest output.

fix

Ensure your code does not rely on elimination of unused variables in object patterns with rest elements (e.g., let { a, ...rest } = obj;).

affects: >=1.0.9

gotchaArrow functions and function expressions are never eliminated because they do not add names to outer scope. Only variable declarators referencing them can be eliminated.

fix

If you rely on elimination of arrow functions, reconsider the design; they are safe from removal.

affects: >=1.0.5

gotchaFor-loop iterator variables (var, let, const) in for...of/for...in are not eliminated since v1.0.7, but earlier versions only preserved var.

fix

Upgrade to >=1.0.8 to ensure const/let iterators are preserved.

affects: <1.0.7

Errors

Common errors & fixes

Cannot find module 'babel-dead-code-elimination'

Package not installed or CommonJS/ESM mismatch (e.g., using require in ESM project).

fix

Run npm install babel-dead-code-elimination. Use import { ... } from 'babel-dead-code-elimination' for ESM, or const { ... } = require('babel-dead-code-elimination') for CommonJS.

TypeError: deadCodeElimination is not a function

Using default import instead of named import.

fix

Use named import: import { deadCodeElimination } from 'babel-dead-code-elimination'.

Cannot use import statement outside a module

Running TypeScript without module configuration or using ESM syntax in CommonJS environment.

fix

Set type: 'module' in package.json or use .mjs extension. Alternatively, use require.

Upgrade

Version history

1.0.12latest on npm

Audit

Dependencies

@babel/parserrequiredRequired for parsing source code into AST in the quickstart example.

@babel/generatorrequiredRequired for generating code from AST after elimination.

@babel/traverseoptionalNeeded when using custom transforms with findReferencedIdentifiers.

Agent activity

20 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/pcattori/babel-dead-code-elimination ↗

packagehttps://www.npmjs.com/package/babel-dead-code-elimination ↗