Domain Model Validation via Proxies

Snippet

Domain Model Validation via Proxies

Proxy objects allow for meta-programming by intercepting fundamental operations. In expert Node.js architectures, they are used to enforce runtime schema validation and data integrity on domain models without polluting the business logic.

snippet.js
javascript
const createSchemaProxy = (target, schema) => {
  return new Proxy(target, {
    set(obj, prop, value) {
      if (schema[prop] && typeof value !== schema[prop]) {
        throw new TypeError(`Property ${prop} must be of type ${schema[prop]}`);
      }
      obj[prop] = value;
      return true;
    }
  });
};
 
const user = createSchemaProxy({}, { age: 'number', name: 'string' });
user.age = 30; // Works
// user.age = '30'; // Throws TypeError

nodejs

Breakdown

set(obj, prop, value) { ... }

The 'set' trap intercepts every attempt to write a property to the target object.

throw new TypeError(...);

Enforces strict type constraints, preventing invalid data from entering the application state.

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Domain Model Validation via Proxies

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