Lot's of small improvements

UI/Base/DropDownUI.ts

@@ -0,0 +1,47 @@
+import {UIEventSource} from "../UIEventSource";
+import {UIElement} from "../UIElement";
+
+export class DropDownUI extends UIElement {
+
+    selectedElement: UIEventSource<string>
+    private _label: string;
+    private _values: { value: string; shown: string }[];
+
+    constructor(label: string, values: { value: string, shown: string }[]) {
+        super(undefined);
+        this._label = label;
+        this._values = values;
+        this.selectedElement = new UIEventSource<string>(values[0].value);
+
+    }
+
+
+    protected InnerRender(): string {
+
+        let options = "";
+        for (const value of this._values) {
+            options += "<option value='" + value.value + "'>" + value.shown + "</option>"
+        }
+
+        return "<form>" +
+            "<label for='dropdown-" + this.id + "'>" + this._label + "</label>" +
+            "<select name='dropdown-" + this.id + "' id='dropdown-" + this.id + "'>" +
+            options +
+            "</select>" +
+            "</form>";
+    }
+
+    InnerUpdate(htmlElement: HTMLElement) {
+        super.InnerUpdate(htmlElement);
+
+        const self = this;
+        const e = document.getElementById("dropdown-" + this.id);
+        e.onchange = function () {
+            // @ts-ignore
+            const selectedValue = e.options[e.selectedIndex].value;
+
+            self.selectedElement.setData(selectedValue);
+        }
+    }
+
+}