mask key

app/javascript/elements/masked_input.js

@@ -0,0 +1,18 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    const maskedToken = this.input.value
+
+    this.input.addEventListener('focus', () => {
+      this.input.value = this.dataset.token
+      this.input.select()
+    })
+
+    this.input.addEventListener('focusout', () => {
+      this.input.value = maskedToken
+    })
+  }
+
+  get input () {
+    return this.querySelector('input')
+  }
+}