optional invite

app/javascript/elements/indeterminate_checkbox.js

@@ -0,0 +1,35 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    if (this.dataset.indeterminate === 'true') {
+      this.checkbox.indeterminate = true
+      this.checkbox.readOnly = true
+    }
+
+    this.checkbox.addEventListener('click', () => {
+      this.checkbox.setAttribute('name', this.dataset.name)
+
+      if (this.showIndeterminateEl) {
+        this.showIndeterminateEl.classList.add('hidden')
+      }
+
+      if (this.checkbox.readOnly) {
+        this.checkbox.checked = this.checkbox.readOnly = false
+      } else if (!this.checkbox.checked) {
+        if (this.showIndeterminateEl) {
+          this.showIndeterminateEl.classList.remove('hidden')
+        }
+
+        this.checkbox.setAttribute('name', this.dataset.indeterminateName)
+        this.checkbox.checked = this.checkbox.readOnly = this.checkbox.indeterminate = true
+      }
+    })
+  }
+
+  get checkbox () {
+    return this.querySelector('input[type="checkbox"]')
+  }
+
+  get showIndeterminateEl () {
+    return document.getElementById(this.dataset.showIndeterminateId)
+  }
+}