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This library is deprecated. It turns out, that the core 6to5 team was working on the same feature in parallel. Starting from version 2.7.0, 6to5 exports a module directly when only the default is exported.

The 6to5 formatter for library authors.

“Author in ES6, distribute everywhere.” Seamlessly target NPM and browsers.


> npm install 6-to-library


1. Write your library

Say your library should uppercase the first letter of a string. You write in ES6 in the file es6/up-first-letter.js:

export default function (string) {
  return string.charAt(0).toLocaleUpperCase() + string.substr(1);
2. Transpile through 6to5's CLI
$ 6to5  --modules 6-to-library  --out-file index.js  es6/up-first-letter.js

Make sure 6to5 is installed globally, or run the local node_modules/6to5/bin/6to5/index.js instead.

…or programatically:

Add the option modules: "6-to-library" to your require("6to5").transform call. You can also pass this option directly to gulp-6to5 or grunt-6to5.

3. Publish your library

npm publish, git push, or whatever you normally do.

4. Profit!

After your users install your library, they can do whatever they're used to. Without any transformer.

Using CommonJS in node:

var upFirstLetter = require("up-first-letter");
upFirstLetter("ęéë");  // » "Ęéë" 

Using globals in the browser:

<script src="bower_components/up-first-letter/index.js"></script>
  upFirstLetter("ęéë");  // » "Ęéë"

Using AMD with RequireJS:

require(["up-first-letter/index"], function (upFirstLetter) {
  upFirstLetter.default("ęéë");  // » "Ęéë" 

And using the shiny new ES6 modules:

import upFirstLetter from "./up-first-letter/es6/up-first-letter";
upFirstLetter("ęéë");  // » "Ęéë" 


You can have a look at the npm module as, built using the 6-to-library formatter.

How does it work

Export/import names

“ECMAScript 6 favors the single/default export style, and gives the sweetest syntax to importing the default.” We do the same. If you only export the default, your library will work as seamlessly as in the examples above.

Otherwise you'll have to reference each export by its specifier:

// original.js 
export default 1;
export const two = 2;
// CommonJS 
var one = require('original').default;
var two = require('original').two;
// Globals 
var one = original.default;
var two = original.two;
Global names

When neither AMD nor CommonJS is supported, properties of the global object will be used as namespaces for every individual file (usually window or global).

The name of the object exported to the global scope is the basename of the module's file, camel-cased.

The name of an object imported from the global scope is the specifier of the default import (only if you're using the syntax import foo from "bar"), or the camel-cased name of the referenced file.

// my-module.js 
import $ from "jquery";  // Maps to window.$ 
import {default as module} from "other-module";  // Maps to window.otherModule 
export default "exported value";  // Maps to window.myModule 
The inner workings

In your transpiled files you get a variation of the UMD module definition, tailor-cut to support all endpoints seamlessly.

For the input file my-module.js:

import {foo as bar} from "./foo-bar";
import baz from "bar";
export default baz[bar];

You get the following output:

(function (global, factory) {
  var root, exportsName, factoryArguments;
  // AMD 
  if (typeof define === "function" && define.amd) {
    define(["exports", "./foo-bar", "bar"], factory);
  } else {
    // CommonJS 
    if (module && typeof module.exports !== "undefined") {
      factoryArguments = [module.exports, require("./foo-bar"), require("bar")];
      root = module;
      exportsName = "exports";
    // Globals 
    } else {
      factoryArguments = [global.myModule = {}, global.fooBar, global.baz];
      root = global;
      exportsName = "myModule";
    factory.apply(null, factoryArguments);
    // If only the default value is exported, may the good be done. 
    if (Object.keys(root[exportsName]).length == 1 && root[exportsName].propertyIsEnumerable("default")) {
      root[exportsName] = root[exportsName]["default"];
})(this, function (exports, _fooBar, _baz) {
  "use strict";
  var _interopRequire = function (obj) {
    return obj && (obj["default"] || obj);
  // Here comes your code. Not much of it in this example. 
  var bar =;
  var baz = _interopRequire(_baz);
  exports["default"] = baz[bar];

(Comments and whitespace added for clarity.)


MIT © Tomek Wiszniewski.