Mefistophell · July 24, 2024 11:32 · Jul 24, 2024
diff --git a/decorator-metadata.ts b/decorator-metadata.ts
@@ -0,0 +1,68 @@
+// Another way is to use const serializables = Symbol();
+const serializables = new WeakMap<object, string[]>();
+
+type Context =
+    | ClassAccessorDecoratorContext
+    | ClassGetterDecoratorContext
+    | ClassFieldDecoratorContext
+    ;
+
+function serialize(_target: any, context: Context): void {
+    if (context.static || context.private) {
+        throw new Error("Can only serialize public instance members.")
+    }
+    if (typeof context.name !== "string") {
+        throw new Error("Can only serialize string properties.");
+    }
+
+    // if Symbol used: const propNames = (context.metadata[serializables] as string[] | undefined) ??= [];
+
+    let propNames = serializables.get(context.metadata || {});
+    if (propNames === undefined) {
+        serializables.set(context.metadata || {}, propNames = []);
+    }
+    propNames.push(context.name);
+}
+function jsonify(instance: object): string {
+
+    // @ts-ignore 
+    const metadata = instance.constructor[Symbol.metadata];
+
+    // if Symbol used: const propNames = metadata?.[serializables] as string[] | undefined;
+    const propNames = metadata && serializables.get(metadata);
+    if (!propNames) {
+        throw new Error("No members marked with @serialize.");
+    }
+    const pairStrings = propNames.map((key: string) => {
+        const strKey = JSON.stringify(key);
+        const strValue = JSON.stringify((instance as any)[key]);
+        return `${strKey}: ${strValue}`;
+    });
+    return `{ ${pairStrings.join(", ")} }`;
+}
+
+
+class Person {
+    firstName: string;
+    lastName: string;
+
+    @serialize
+    age: number
+
+    @serialize
+    get fullName() {
+        return `${this.firstName} ${this.lastName}`;
+    }
+    toJSON() {
+        return jsonify(this)
+    }
+    constructor(firstName: string, lastName: string, age: number) {
+        this.firstName = firstName
+        this.lastName = lastName
+        this.age = age
+    }
+}
+
+const person = new Person('Alice', 'Sofia', 4)
+
+console.log(person.toJSON())