Fix Webpack global scope issue

[giacomodeliberali]

In webpack 4 (Angular 8)

var _global = (function () {
	return this;
})();

will return undefined causing "Cannot read property WebSocket of undefined".

Resolves #287.

[ibc]

Makes sense. Merged, thanks.

[michaelsbradleyjr]

I realize this has been merged already but for a bit more resilience how about:

var _global = (function () {
  if (!this) {
    if (typeof global !== 'undefined') {
      return global;
    }
    if (typeof globalThis !== 'undefined') {
      return globalThis;
    }
    if (typeof self !== 'undefined') {
      return self;
    }
    if (typeof window !== 'undefined') {
      return window;
    }
    throw new Error('could not determine the global object');
  }
  return this;
})();

See: https://github.com/tc39/proposal-global#rationale.

[michaelsbradleyjr]

There's actually a viable polyfill for globalThis:

(function() {
  if (typeof globalThis === 'object') return;
  try {
    Object.defineProperty(Object.prototype, '__magic__', {
      get: function() {
        return this;
      },
      configurable: true
    });
    __magic__.globalThis = __magic__;
    // The previous line should have made `globalThis` globally
    // available, but it fails in Internet Explorer 10 and older.
    // Detect this failure and fall back.
    if (typeof globalThis === 'undefined') {
      // Assume `window` exists.
      window.globalThis = window;
    }
    delete Object.prototype.__magic__;
  } catch (error) {
    // In IE8, Object.defineProperty only works on DOM objects.
    // If we hit this code path, assume `window` exists.
    window.globalThis = window;
  }
}());

See: https://mathiasbynens.be/notes/globalthis.

Node 12 and current Chrome, Firefox, and Safari all already implement globalThis. So instead of defining _global you could plop in this polyfill and then refer to globalThis instead of _global.