uglify.js

// A standalone script that replicates the preprocessing stage in box-js.

const unsafe = true;
const code = require("fs").readFileSync(process.argv[2], "utf8");
const result = require("uglify-es").minify(code, {
	compress: {
		passes: 3,

		booleans: true,
		cascade: true,
		collapse_vars: true,
		comparisons: true,
		conditionals: true,
		dead_code: true,
		drop_console: false,
		evaluate: true,
		if_return: true,
		inline: true,
		join_vars: false, // readability
		keep_fargs: unsafe, // code may rely on Function.length
		keep_fnames: unsafe, // code may rely on Function.prototype.name
		keep_infinity: true, // readability
		loops: true,
		negate_iife: false, // readability
		properties: true,
		pure_getters: false, // many variables are proxies, which don't have pure getters
		/* If unsafe preprocessing is enabled, tell uglify-es that Math.* functions
		 * have no side effects, and therefore can be removed if the result is
		 * unused. Related issue: mishoo/UglifyJS2#2227
		 */
		pure_funcs: unsafe ?
			// https://stackoverflow.com/a/10756976
			Object.getOwnPropertyNames(Math).map(key => `Math.${key}`) :
			null,
		reduce_vars: true,
		/* Using sequences (a; b; c; -> a, b, c) provides some performance benefits
		 * (https://github.com/CapacitorSet/box-js/commit/5031ba7114b60f1046e53b542c0e4810aad68a76#commitcomment-23243778),
		 * but it makes code harder to read. Therefore, this behaviour is disabled.
		 */
		sequences: false,
		toplevel: true,
		typeofs: false, // typeof foo == "undefined" -> foo === void 0: the former is more readable
		unsafe,
		unused: true,
	},
	output: {
		beautify: true,
		comments: true,
	},
});
console.log(result.code);