Bootstrap: support native es6 module loading

[rpokrovskij]

Bootstrap 4.3 (budnle from dist folder) fails when global is null.

From sources:

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('jquery'), require('popper.js')) :
  typeof define === 'function' && define.amd ? define(['exports', 'jquery', 'popper.js'], factory) :
  (factory((global.bootstrap = {}),global.jQuery,global.Popper));
}(this, (function (exports,$,Popper) {...});

There this from next line can't be null since we will get an excpetion on global.bootstrap = {}

And there are situations when this can be null during loading e.g. importing using native module support:

```

```

Check sources of jquery. They support this new type of loading by checking (this==null)?window:this.

[Johann-S]

About that we should ship an ESM version of Bootstrap

[rpokrovskij]

It seems it was rollup problem
Now when you have updated rollup.js code looks like

(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('jquery'), require('popper.js')) :
  typeof define === 'function' && define.amd ? define(['exports', 'jquery', 'popper.js'], factory) :
  (global = global || self, factory(global.bootstrap = {}, global.jQuery, global.Popper));
}(this, function (exports, $, Popper) { 'use strict';

so there we have global = global || self

Self there is Window.self (HTML5) ... I've not tested how it works, but I could propose other problem would be to obtain global.Popper (global.jQuery is ok)

you will find that popper esm register itself as global.popper (low case)

[Johann-S]

Hmm yep, that's why I think we should ship an ESM version of Bootstrap not just UMD

[KayakinKoder]

Sorry to interject, but does this mean bootstrap can't be built with an ES module bundler like Rollup?

[Johann-S]

Hi @KayakinKoder absolutly not, Rollup or Webpack prefer ESM build but if there is no ESM build they use the UMD one (for Bootstrap) 😉

BTW this issue is solved by: https://github.com/twbs/bootstrap/pull/28386

And will be in our v5