Property Schema Decorator

propertySchema.ts

function propertySchema(schema: Schema) {
  return function(target: Object, key: string | symbol): void {
    // The property
    let val = target[key];
    let propertyName = String(key);

    // Generate getter and setter
    const getter = () => {
      return val;
    };
    const setter = value => {
      // Validate
      const { error } = schema.validate(value);
      // Throw an error if validation fails
      if (error instanceof Error) {
        // A descriptive error message
        error.message = error.message.replace('"value"', `"${propertyName}"`);
        throw error;
      }
      // Else, set value
      val = value;
    };
    // Append getter and setter to the target
    Object.defineProperty(target, key, {
      get: getter,
      set: setter,
      enumerable: true,
      configurable: true
    });
  };
}