@tir.jp/is-dev

Lightweight environment detection and assertions optimized for tree-shaking and dead code elimination in bundlers like esbuild.

This module provides constants and functions that can be completely removed from your production build when used with a bundler that supports dead code elimination (e.g., esbuild, rollup, webpack).

Installation

npm install @tir.jp/is-dev

Features

isDev and isProd

Detects the current environment. It looks for IS_DEV or IS_PROD global variables (defined via bundler define plugins). If neither is defined, isDev defaults to true.

import { isDev, isProd } from '@tir.jp/is-dev';

if (isDev) {
  console.log('Running in development mode');
}

if (isProd) {
  // This block and the check itself can be eliminated in production
  // if IS_DEV/IS_PROD are defined as constants.
}

assert(condition, message)

A simple assertion function. In production mode, it becomes an empty function and can be completely removed by your bundler.

import { assert } from '@tir.jp/is-dev';

assert(value > 0, 'value must be positive');

assertOnlyValidParams(invalids)

Checks if an object (typically containing "rest" parameters) is empty. Useful for catching typos in parameter objects during development without any production overhead.

import { assertOnlyValidParams } from '@tir.jp/is-dev';

function myFunction(params) {
  const { foo, bar, ...invalids } = params || {};
  assertOnlyValidParams(invalids);
  
  // Logic using foo and bar...
}

Production Optimization (e.g., esbuild)

To achieve full code elimination, define IS_DEV or IS_PROD as constants in your bundler configuration.

esbuild example

esbuild app.js --bundle --minify --define:IS_DEV=false --outfile=out.js

In this case, isDev becomes false at compile time, and all isDev blocks and assert calls will be removed from the final bundle.

License

Zlib