Data types-related fixes

js/entity/Identifier.js

@@ -0,0 +1,32 @@
+import IEntity from "./IEntity"
+
+
+export default class Identifier extends IEntity {
+
+    static attributes = {
+        value: String,
+    }
+
+    constructor(options = {}) {
+        // Not instanceof to pick also primitive string
+        if (options.constructor === String) {
+            options = {
+                value: options
+            }
+        }
+        super(options)
+        /** @type {String} */
+        this.value
+        if (!this.value.match(/\w+/)) {
+            throw new Error("The value must be an identifier (/\w+/).")
+        }
+    }
+
+    valueOf() {
+        return this.value
+    }
+
+    toString() {
+        return this.value
+    }
+}