Update plugin loading for headless option

.eslintrc

@@ -4,7 +4,7 @@
     "node": true
   },
   "parserOptions": {
-    "ecmaVersion": 2018,
+    "ecmaVersion": 2020,
     "sourceType": "module"
   },
   "rules": {

src/index.js

@@ -2,6 +2,7 @@ import { isElement, isFunction } from 'underscore';
 import $ from 'utils/cash-dom';
 import Editor from './editor';
 import polyfills from 'utils/polyfills';
+import { getGlobal } from 'utils/mixins';
 import PluginManager from './plugin_manager';
 
 polyfills();
@@ -57,13 +58,13 @@ export default {
 
     // Load plugins
     config.plugins.forEach(pluginId => {
-      let plugin = plugins.get(pluginId);
+      let plugin = isFunction(pluginId) ? pluginId : plugins.get(pluginId);
       const plgOptions = config.pluginsOpts[pluginId] || {};
 
       // Try to search in global context
       if (!plugin) {
-        const wplg = window[pluginId];
-        plugin = wplg && wplg.default ? wplg.default : wplg;
+        const wplg = getGlobal()[pluginId];
+        plugin = wplg?.default || wplg;
       }
 
       if (plugin) {

src/utils/mixins.js

@@ -1,7 +1,16 @@
 import { keys, isUndefined, isElement, isArray } from 'underscore';
 
+export const isDef = value => typeof value !== 'undefined';
+
 export const hasWin = () => typeof window !== 'undefined';
 
+export const getGlobal = () =>
+  typeof globalThis !== 'undefined'
+    ? globalThis
+    : typeof window !== 'undefined'
+    ? window
+    : global;
+
 export const toLowerCase = str => (str || '').toLowerCase();
 
 const elProt = hasWin() ? window.Element.prototype : {};