Initial *build()* support for Tabs.

Issue #258.

␄

lib/widget.js

@@ -2154,6 +2154,33 @@ window.NexusHoratio.widget = (function widget() {
     /** @param {string} name - Name for this instance. */
     constructor(name) {
       super(name, 'tabs');
+      this.on('build', this.#onBuild)
+        .on('destroy', this.#onDestroy);
+    }
+
+    #tablist
+
+    #resetContainer = () => {
+      this.container.innerHTML = '';
+      this.#tablist = document.createElement('tablist');
+      this.#tablist.role = 'tablist';
+      this.container.append(this.#tablist);
+    }
+
+    #onBuild = (...rest) => {
+      const me = 'onBuild';
+      this.logger.entered(me, rest);
+
+      this.#resetContainer();
+
+      this.logger.leaving(me);
+    }
+
+    #onDestroy = (...rest) => {
+      const me = 'onDestroy';
+      this.logger.entered(me, rest);
+
+      this.logger.leaving(me);
     }
 
   }
@@ -2169,6 +2196,23 @@ window.NexusHoratio.widget = (function widget() {
       this.assertEqual(w.container.tagName, 'TABS', 'correct element');
     }
 
+    testEmptyBuild() {
+      // Assemble
+      const w = new Tabs(this.id);
+
+      // Act
+      w.build();
+
+      // Assert
+      const expected = [
+        `^<tabs id="Tabs-[^-]*-${GUID}[^"]*">`,
+        '<tablist role="tablist">',
+        '</tablist>',
+        '</tabs>$',
+      ].join('');
+      this.assertRegExp(w.container.outerHTML, RegExp(expected, 'u'));
+    }
+
   }
   /* eslint-enable */