IIFE generator

$async IIFE generator enables to easily create a pre-concatenated selection of $async modules that is additionally optimized using Google Closure Compiler.

The generator is available online on https://style.tools/iife/

What is IIFE?

IIFE or Immediately-invoked Function Expressions is a coding pattern for loading a script. An IIFE can be used in the browser safely.


<script async src="js/async-iife.js" data-c='[
"href": "https://cdn.com/css/sheet2.css",
"render_timing": "requestAnimationFrame"

The IIFE can be optmized using Google Closure Compiler with Advanced Optimizations for optimal compression.

The Node.js module can be executed as a CLI program from the command-line.


npm install @style.tools/async-iife



The provided iife-cli.js script can be used from the command-line. The NPM package contains a npm run iife script.


Display usage information and a list with available modules.

npm run iife -- --help
CLI program help

The following command shows how to create an IIFE with unary format, output to path/to/iife.js and with 3 modules that automatically load the required dependencies.

npm run iife -- --format unary --compress --output path/to/iife.js --modules css-loader,localstorage,timing

Short flags and a space separated module list are supported.

npm run iife -- -f unary -c -o path/to/iife.js -m "css-loader localstorage timing"

When omitting the --output flag the script is printed to the console, e.g. for > output.js.

Node.js module

// load Node.js module
const iife = require('@style.tools/async-iife');
// return script text for inlining
// uses memory-cache @link https://www.npmjs.com/package/memory-cache
iife.generate(['css-loader', 'timing'], {
debug: true, // debug sources
format: 'unary' // !function(){ ... }()
}).then(function(iife_script) {
// iife_script contains the IIFE script text
// output to file
iife.generate(['css-loader', 'timing'], {
compress: true, // Google Closure Compiler API compression
format: 'wrap', // (function(){ ... })()
output: 'path/to/iife.js',
output_stats: true // return { modules:[], size:0, gzip_size:0 }
}).then(function(stats) {
// iife.js written

The Node.js module can be used efficiently within a Node.js CMS. IIFE's are cached in memory using memory-cache.

Warning: the generator depends on the free Google Closure Compiler API that may not be 100% reliable. When using the generator in production it may be an option to use a local Google Closure Compiler service.