autoresize textarea

app/javascript/elements/autoresize_textarea.js

@@ -0,0 +1,17 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    this.resize()
+
+    this.textarea.addEventListener('input', () => this.resize())
+  }
+
+  resize () {
+    if (this.textarea.clientHeight < this.textarea.scrollHeight) {
+      this.textarea.style.height = `${this.textarea.scrollHeight}px`
+    }
+  }
+
+  get textarea () {
+    return this.querySelector('textarea')
+  }
+}