Add initial versions

lazy-imports.js

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+/**
+@license
+Copyright (c) 2022 trading_peter
+This program is available under Apache License Version 2.0
+*/
+
+/**
+ * Used to import other scripts dynamically based on a route change from the-router for example.
+ * Do this by defining lazyMap for the importer and then calling `import` with the new path segments.
+ *
+ * ## Example lazyMp
+ *
+ * ```js
+ * [
+ *    {
+ *      match: /^user$/,  // Would match /user/
+ *      imports: [ 'user-element-1.html', 'user-element-2.html' ],
+ *      map: [
+ *        {
+ *          match: /^settings$/,  // Would match /user/settings
+ *          imports: [ 'settings.html' ]
+ *        }
+ *      ]
+ *     }
+ * ]
+ * ```
+ *
+ * Use the _lazyImport method to start processing the map.
+ * _lazyImport needs an array of strings that describe the path segments it should
+ * match the map and sub maps against.
+ *
+ * So, if for example your route is /user/settings you need to split
+ * the path to [ 'user', 'settings' ] and feed it to the _lazyImport function.
+*/
+export default class {
+  constructor(lazyMap) {
+    this.lazyMap = lazyMap;
+  }
+
+  import(segments) {
+    if (typeof segments === 'object' && !Array.isArray(segments)) {
+      segments = Object.values(segments).filter(v => v !== undefined);
+    }
+
+    if (!this.lazyMap || !Array.isArray(segments)) return;
+
+    const imports = [];
+    this.__processLazyMap(this.lazyMap, segments, 0, imports);
+
+    const promises = imports.map(url => {
+      return import(url);
+    });
+
+    return promises.length === 1 ? promises[0] : Promise.all(promises);
+  }
+
+  __processLazyMap(map, segments, level, list) {
+    const segment = segments[level];
+    if (segment === undefined) return [];
+
+    map.forEach(entry => {
+      if (!entry.match.test(segment)) return;
+
+      if (Array.isArray(entry.imports)) {
+        if (entry.match.test(segment)) {
+          list.push(...entry.imports);
+        }
+      }
+
+      if (Array.isArray(entry.map)) {
+        this.__processLazyMap(entry.map, segments, level + 1, list);
+      }
+    });
+  }
+}