Schema validation ensures that the data being processed conforms to a defined structure or schema. By validating data against a predefined schema, we can catch errors early on and provide a more robust and secure system.

To get started, let’s first define the schema for the data we want to validate. For this example, let’s consider a simple user schema with properties like name, age, and email.

const userSchema = {
  name: String,
  age: Number,
  email: String,
};

Now, we can create a proxy validation function that takes an object and a schema as arguments. The proxy will intercept property assignments and validate them against the schema.

function createValidationProxy(obj, schema) {
  return new Proxy(obj, {
    set(target, property, value) {
      const propertyType = schema[property];

      if (typeof value === propertyType) {
        target[property] = value;
      } else {
        throw new Error(`Invalid data type for property ${property}`);
      }

      return true;
    },
  });
}

In the above code, we create a proxy using the new Proxy() constructor. Inside the proxy’s set() trap, we check if the type of the incoming value for a given property matches the expected type defined in the schema. If there’s a mismatch, we throw an error; otherwise, we set the property value on the target object.

Let’s see the validation proxy in action:

const user = createValidationProxy({}, userSchema);

user.name = "John Doe";
user.age = 30;
user.email = "john.doe@example.com";

console.log(user); // { name: 'John Doe', age: 30, email: 'john.doe@example.com' }

user.name = true; // Throws an error: Invalid data type for property name

As you can see, the proxy ensures that only values of the correct data type can be assigned to the respective properties. If we try to assign a value of a different data type, an error is thrown, alerting us to the invalid assignment.

By using a proxy-based schema validation approach like this, we have a powerful tool at our disposal to validate and ensure the integrity of our data structures. This technique can be extended to handle more complex schemas and provide custom validation rules as needed.

With schema validation in place, we can confidently process user inputs, API responses, and any other data sources, knowing that we are working with consistent and valid data.

#JavaScript #SchemaValidation