chore: promises store resolved values

So make use of this!

Author: feildmaster

changelog.md

@@ -1,7 +1,7 @@
 # UnderScript App Changelog
 
 ## Version 1.4.0 (2020-03-06)
-1. Fixed UnderScript so it can actually update
+1. Can now update UnderScript without having to restart
 1. URL's now open in browser
 1. Remember Me now shows that it does something in the app
 

src/preload/plugin.js

@@ -1,28 +1,26 @@
 const { ipcRenderer } = require('electron');
 
-const promise = new Promise((res) => {
+// Acts as a cache for the resulting plugin
+const plugin = new Promise((res) => {
   document.addEventListener('DOMContentLoaded', () => {
-    plugin = underscript.plugin('UnderScript App');
-    res(plugin);
-  }, { once: true });
+    res(underscript.plugin('UnderScript App'));
+  });
 });
 
-let plugin;
 function getPlugin() {
-  if (plugin) return Promise.resolve(plugin);
-  return promise;
+  return Promise.resolve(plugin); // Hand out a fresh promise
 }
 
 ipcRenderer.on('toast', (_, data) => {
   getPlugin().then((plugin) => {
+    if (!plugin) return; // Should never happen, but who knows
     if (data.refresh) {
       data.onClose = (...args) => {
         location.reload();
       };
       delete data.refresh;
     }
     plugin.toast(data);
-    return plugin;
   });
 });