babel-plugin-transform-dead-code-elimination

2.2.3 verified Sat Apr 25 auth: no javascript deprecated

A Babel 6 plugin that eliminates dead (unreachable) code, including unused variables, unreachable statements, and dead logical operators. It is a fork of babel-plugin-dead-code-elimination with additional fixes and features. Current stable version is v2.2.3, with releases in 2016 (last release 2.2.3). It is specific to Babel 6 and not compatible with Babel 7+. Key differentiators: supports experimental inlining (but warns it may break code), handles hoisted async functions correctly, and properly eliminates repeated var/function declarations.

Common errors

error Error: Plugin transform-dead-code-elimination requires a Babel 6 version ↓

cause Using plugin with Babel 7 or later.

fix

Use @babel/plugin-transform-dead-code-elimination for Babel 7.

error AssertionError [ERR_ASSERTION]: false == true ↓

cause Bug with repeated var/function declarations in older versions.

fix

Upgrade to version 2.2.2 or later.

Warnings

gotcha experimentalInlining option can break code; use with caution. ↓

fix Avoid setting experimentalInlining: true unless you thoroughly test output.

deprecated This plugin is for Babel 6 only. Not compatible with Babel 7+. ↓

fix Use @babel/plugin-transform-dead-code-elimination or equivalent for Babel 7.

gotcha Plugin may incorrectly eliminate hoisted async functions if transform-async-to-generator is not used. ↓

fix Upgrade to version 2.2.1 or later.

Install

npm install babel-plugin-transform-dead-code-elimination

yarn add babel-plugin-transform-dead-code-elimination

pnpm add babel-plugin-transform-dead-code-elimination

Imports

default

wrong

const plugin = require('babel-plugin-transform-dead-code-elimination')

correct

import plugin from 'babel-plugin-transform-dead-code-elimination'

This is a Babel plugin, not commonly imported directly; typically used in .babelrc or babel.config.js as a string.

Quickstart

Demonstrates using the plugin to eliminate dead code (unreachable branch and unused variable).

// .babelrc
{
  "plugins": [
    "transform-dead-code-elimination"
  ]
}

// Input: dead code
function example() {
  if (false) {
    return 1;
  }
  return 2;
  var x = 3; // unused
}

// Output: dead code removed
function example() {
  return 2;
}