@esm.sh/cjs-module-lexer
v1.0.7
Published
A lexer for detecting the `module.exports` of a CJS module.
Downloads
412
Readme
cjs-module-lexer
A lexer for detecting the module.exports
of a CJS module, written in Rust.
Installation
You can install cjs-module-lexer via npm CLI:
npm i @esm.sh/cjs-module-lexer
Usage
cjs-module-lexer provides a parse
function that detects the module.exports
of a commonjs module. The function returns an object with two properties: exports
and reexports
. The exports
property is an array of the exported names, and the reexports
property is an array of the reexported modules.
import { parse } from "@esm.sh/cjs-module-lexer";
// named exports by assignment
// exports: ["a", "b", "c", "__esModule", "foo"]
const { exports } = parse("index.cjs", `
exports.a = "a";
module.exports.b = "b";
Object.defineProperty(exports, "c", { value: 1 });
Object.defineProperty(module.exports, "__esModule", { value: true })
const key = "foo"
Object.defineProperty(exports, key, { value: "e" });
`);
// reexports
// reexports: ["./lib"]
const { reexports } = parse("index.cjs", `
module.exports = require("./lib");
`);
// object exports(spread syntax supported)
// exports: ["foo", "baz"]
// reexports: ["./lib"]
const { exports, reexports } = parse("index.cjs", `
const foo = "bar"
const obj = { baz: 123 }
module.exports = { foo, ...obj, ...require("./lib") };
`);
// if expression
// exports: ["foo", "cjs"]
const { exports } = parse("index.cjs", `
module.exports.a = "a";
if (true) {
exports.foo = "bar";
}
const mtype = "cjs";
if (mtype === "cjs") {
exports.cjs = true;
} else {
exports.esm = true;
}
if (false) {
exports.unreachable = true;
}
`);
// condition exports by checking if `process.env.NODE_ENV` equals to `nodeEnv` option
// reexports: ["./index.development.js"]
const { reexports } = parse("index.cjs", `
if (process.env.NODE_ENV === "development") {
module.exports = require("./index.development.js")
} else {
module.exports = require("./index.production.js")
}
`, { nodeEnv: "development" });
// block&IIFE
// exports: ["foo", "baz", "__esModule"]
const { exports } = parse("index.cjs", `
{
exports.foo = 'bar'
}
(function () {
exports.baz = 'qux'
if (true) {
return
}
exports.unreachable = true
})();
exports.__esModule = true
`);
// UMD format
// exports: ["foo"]
const { exports } = parse("index.cjs", `
(function (global, factory) {
typeof exports === "object" && typeof module !== "undefined" ? factory(exports) :
typeof define === "function" && define.amd ? define(["exports"], factory) :
(factory((global.MMDParser = global.MMDParser || {})));
}(this, function (exports) {
exports.foo = "bar";
}))
`);
// exports by calling a function
// exports: ["foo"]
const { exports } = parse("index.cjs", `
function module() {
return { foo: "bar" }
}
module.exports = module()
`);
// annotated export names for ESM import
// exports: ["foo", "bar"]
const { exports } = parse("lib.cjs", `
0 && (module.exports = {
foo,
bar,
})
`);
// call reexports
// reexports: ["./lib()"]
const { reexports } = parse("index.cjs", `
module.exports = require("./lib")()
`);
// apply call reexports
// exports: ["foo"]
const { exports } = parse("lib.cjs", `
module.exports = function() {
return { foo: "bar" }
}
`, { callMode: true });
The parse
function has the following types definition:
export function parse(
specifier: string,
code: string,
options? {
nodeEnv?: 'development' | 'production',
callMode?: boolean,
}
): {
exports: string[],
reexports: string[],
};