add Slidesshow.js

js/Slideshow.js

+export class Slideshow {
+
+    constructor(image, element) {
+        this.images = image.split(',');
+        this.element = element;
+        this._index = 0;
+        this.show(this.images[this._index]);
+    }
+
+    show(image) {
+        this.element.html(`<a href="images/${image}.gif">
+        <img src="images/${image}.gif" /></a>`);
+    }
+
+    next() {
+        this._index = this._index + 1 < this.images.length ? this._index + 1 : 0;
+        this.show(this.images[this._index]);
+    }
+
+    prev() {
+        this._index = this._index - 1 > -1 ? this._index - 1 : this.images.length - 1;
+        this.show(this.images[this._index]);
+    }
+
+    get index() {
+        return this._index;
+    }
+
+}
\ No newline at end of file