refactor: Still trying to reorganize edit mode to be more robust

node_modules/tldts-core/src/domain-without-suffix.ts

@@ -0,0 +1,14 @@
+/**
+ * Return the part of domain without suffix.
+ *
+ * Example: for domain 'foo.com', the result would be 'foo'.
+ */
+export default function getDomainWithoutSuffix(
+  domain: string,
+  suffix: string,
+): string {
+  // Note: here `domain` and `suffix` cannot have the same length because in
+  // this case we set `domain` to `null` instead. It is thus safe to assume
+  // that `suffix` is shorter than `domain`.
+  return domain.slice(0, -suffix.length - 1);
+}