From https://once.com/writebook

app/javascript/controllers/web_share_controller.js

@@ -0,0 +1,36 @@
+import { Controller } from "@hotwired/stimulus"
+
+export default class extends Controller {
+  static values = { title: String, text: String, url: String, files: String }
+
+  connect() {
+    this.element.hidden = !navigator.canShare
+  }
+
+  async share() {
+    await navigator.share(await this.#getShareData())
+  }
+
+  async #getShareData() {
+    const data = { title: this.titleValue, text: this.textValue }
+
+    if (this.urlValue) {
+      data.url = this.urlValue
+    }
+
+    if (this.filesValue) {
+      data.files = [ await this.#getFileObject()]
+    }
+
+    return data;
+  }
+
+  async #getFileObject() {
+    const response = await fetch(this.filesValue)
+    const blob = await response.blob()
+    const randomPrefix = `Writebook_${Math.random().toString(36).slice(2)}`
+    const fileName = `${randomPrefix}.${blob.type.split('/').pop()}`
+
+    return new File([ blob ], fileName, { type: blob.type })
+  }
+}