Util cleanup

StringMap.js

@@ -0,0 +1,17 @@
+class StringMap extends Map {
+  has(key) {
+    return super.has(key.toString());
+  }
+
+  get(key) {
+    return super.get(key.toString());
+  }
+
+  set(key, value) {
+    return super.set(key.toString(), value);
+  }
+
+  delete(key) {
+    return super.delete(key.toString());
+  }
+}