diff --git a/javascript/simpleProgressBar.js b/javascript/simpleProgressBar.js
new file mode 100644
index 000000000..75cbfe49c
--- /dev/null
+++ b/javascript/simpleProgressBar.js
@@ -0,0 +1,82 @@
+class SimpleProgressBar {
+  #container = document.createElement("div");
+  #progress = document.createElement("div");
+  #textDiv = document.createElement("div");
+  #text = document.createElement("span");
+  #visible = false;
+  #hideTimeout = null;
+  #interval = null;
+  #max = 0;
+  /** @type {Set} */
+  #monitoredSet;
+
+  constructor() {
+    this.#container.style.cssText = "position:relative;width:100%;background-color:hsla(0,0%,36%,0.3);height:1.2rem;margin:0;padding:0;display:none;"
+    this.#progress.style.cssText = "position:absolute;left:0;height:100%;width:0;transition:width 200ms;"
+    this.#progress.style.backgroundColor = "hsla(110, 32%, 35%, 0.80)";  // alt: "#27911d"
+    this.#textDiv.style.cssText = "margin:auto;width:max-content;height:100%;";
+    this.#text.style.cssText = "position:relative;user-select:none;color:white;"
+
+    this.#textDiv.append(this.#text);
+    this.#container.append(this.#progress, this.#textDiv);
+  }
+
+  setMax(max) {
+    this.clearProgress();
+    this.#max = max;
+    this.#startUpdating();
+  }
+
+  attach(element) {
+    if (element.hasChildNodes) {
+      element.innerHTML = '';
+    }
+    element.appendChild(this.#container);
+  }
+
+  monitor(hashes) {
+    // This is required because incrementing a variable with a class method turned out to not be an atomic operation
+    this.#monitoredSet = hashes;
+  }
+
+  clearProgress() {
+    this.#stopUpdating();
+    clearTimeout(this.#hideTimeout);
+    this.#hideTimeout = null;
+    this.#container.style.display = "none";
+    this.#visible = false;
+    this.#progress.style.width = "0";
+    this.#text.textContent = "";
+  }
+
+  #setProgress(loaded, max) {
+    if (this.#hideTimeout) {
+      this.#hideTimeout = null;
+    }
+
+    this.#progress.style.width = `${Math.floor((loaded / max) * 100)}%`;
+    this.#text.textContent = `${loaded}/${max}`;
+
+    if (!this.#visible) {
+      this.#container.style.display = "block";
+      this.#visible = true;
+    }
+    if (loaded >= max) {
+      this.#stopUpdating()
+      this.#hideTimeout = setTimeout(() => {
+        this.clearProgress();
+      }, 1000);
+    }
+  }
+
+  #startUpdating() {
+    this.#interval = setInterval(() => {
+      this.#setProgress(this.#monitoredSet.size, this.#max);
+    }, 250);
+  }
+
+  #stopUpdating() {
+    clearInterval(this.#interval);
+    this.#interval = null;
+  }
+}