abstract dynamic video tile load within new dynamicloader class to allow to load other elements dynamically.

src/elements/DynamicContentContainer/DynamicContentContainer.tsx

@@ -0,0 +1,87 @@
+import React from 'react';
+import style from './DynamicContentContainer.module.css';
+
+interface Props<T> {
+    renderElement: (elem: T) => JSX.Element;
+    data: T[];
+    initialLoadNr?: number;
+}
+
+interface state<T> {
+    loadeditems: T[];
+    selectionnr: number;
+}
+
+/**
+ * A videocontainer storing lots of Preview elements
+ * includes scroll handling and loading of preview infos
+ */
+class DynamicContentContainer<T> extends React.Component<Props<T>, state<T>> {
+    // stores current index of loaded elements
+    loadindex: number = 0;
+
+    constructor(props: Props<T>) {
+        super(props);
+
+        this.state = {
+            loadeditems: [],
+            selectionnr: 0
+        };
+    }
+
+    componentDidMount(): void {
+        document.addEventListener('scroll', this.trackScrolling);
+
+        this.loadPreviewBlock(this.props.initialLoadNr ? this.props.initialLoadNr : 16);
+    }
+
+    render(): JSX.Element {
+        return (
+            <div className={style.maincontent}>
+                {this.state.loadeditems.map((elem) => {
+                    return this.props.renderElement(elem);
+                })}
+                {/*todo css for no items to show*/}
+                {this.state.loadeditems.length === 0 ? 'no items to show!' : null}
+                {this.props.children}
+            </div>
+        );
+    }
+
+    componentWillUnmount(): void {
+        // unbind scroll listener when unmounting component
+        document.removeEventListener('scroll', this.trackScrolling);
+    }
+
+    /**
+     * load previews to the container
+     * @param nr number of previews to load
+     */
+    loadPreviewBlock(nr: number): void {
+        let ret = [];
+        for (let i = 0; i < nr; i++) {
+            // only add if not end
+            if (this.props.data.length > this.loadindex + i) {
+                ret.push(this.props.data[this.loadindex + i]);
+            }
+        }
+
+        this.setState({
+            loadeditems: [...this.state.loadeditems, ...ret]
+        });
+
+        this.loadindex += nr;
+    }
+
+    /**
+     * scroll event handler -> load new previews if on bottom
+     */
+    trackScrolling = (): void => {
+        // comparison if current scroll position is on bottom --> 200 is bottom offset to trigger load
+        if (window.innerHeight + document.documentElement.scrollTop + 200 >= document.documentElement.offsetHeight) {
+            this.loadPreviewBlock(8);
+        }
+    };
+}
+
+export default DynamicContentContainer;