From https://once.com/writebook

app/javascript/controllers/upload_preview_controller.js

@@ -0,0 +1,20 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static values = { defaultImage: String }
+  static targets = [ "image", "input", "button" ]
+
+  previewImage() {
+    const file = this.inputTarget.files[0]
+
+    if (file) {
+      this.imageTarget.src = URL.createObjectURL(this.inputTarget.files[0]);
+      this.imageTarget.onload = () => { URL.revokeObjectURL(this.imageTarget.src) }
+    }
+  }
+
+  clear() {
+    this.imageTarget.src = this.defaultImageValue
+    this.buttonTarget.style.visibility = "hidden"
+  }
+}