babel-dead-code-elimination

Composable primitives for dead code elimination in Babel

This package is not a Babel plugin, but rather a set of composable primitives to author your own Babel transforms and plugins.

Install

1npm install babel-dead-code-elimination

deadCodeElimination

Eliminates unused code from the Babel AST by repeatedly removing unreferenced identifiers.

1import { parse } from "@babel/parser"
2import generate from "@babel/generator"
3
4import { deadCodeElimination } from "babel-dead-code-elimination"
5
6let source = "..."
7let ast = parse(source, { sourceType: "module" })
8deadCodeElimination(ast)
9let result = generate(ast).code

findReferencedIdentifiers

Find identifiers that are currently referenced in the Babel AST.

Useful for limiting deadCodeElimination to only eliminate newly unreferenced identifiers, as a best effort to preserve any intentional side-effects in the source.

1import { parse } from "@babel/parser"
2import generate from "@babel/generator"
3import traverse from "@babel/traverse"
4
5import {
6  deadCodeElimination,
7  findReferencedIdentifiers,
8} from "babel-dead-code-elimination"
9
10let source = "..."
11let ast = parse(source, { sourceType: "module" })
12let referenced = findReferencedIdentifiers(ast)
13
14traverse(ast, {
15  /* ... your custom transform goes here ... */
16})
17
18deadCodeElimination(ast, referenced)
19let result = generate(ast).code

Prior art

Credit to Jason Miller for the initial implementation. Thanks to these projects for exploring dead code elimination:

• Next.js
• babel-plugin-eliminator
• bling