aev - Another Express Validator

aev makes use of Ajv JSON schema validator to provide a fast and easy to use request validation middleware for your express application.

The Ajv documentation can be found on the official website: https://ajv.js.org

Installation

npm i aev

Usage

1. Create JSON schema

Create a schema file that contains all methods you want to validate. Since aev finds the definition by req.method you have to name your properties accordingly.

For each method aev can validate all properties in the express request object like params, query and body. However, they are optional in your definition.

// requests.schema.json

{
    "GET": {
        "type": "object",
        "properties": {
            "params": {
                "type": "object",
                "additionalProperties": false,
                "properties": {
                    "id": {
                        "type": "integer",
                    },
                }
            },
            "query": {
                "type": "object",
                "additionalProperties": false,
                "properties": {
                    "search": {
                        "type": "string",
                    }
                }
            }
        }
    },

    "POST": {
        ...
    },
    "PUT": {
        ...
    }
    ...
}

2. Require aev

Require your schema file, require aev and pass in that schema. This is all we need.

const schema = require("requests.schema");
const validateRequest = require("aev")(schema);

3. Use middleware

Just use it like every other middleware. aev identifies the required schema by request method, so we do not have to worry about it when calling it:

// exampleRouter.js

router.get("/example", validateRequest, (req, res, next) => {
    // ...
}

4. Handle errors

aev calls next() with one of three custom errors. You can handle them in an error handler middleware like so:

// app.js

app.use(async (error, req, res, next) => {
    if (error.name === "RequestInvalidError") {
        // ...
    }
});

RequestInvalidError

When validation fails, RequestInvalidError provides additional information as an Array error.invalidProps with all invalid request properties as Objects. Each contains the occurence and message as well as error.params from Ajv test errors. For more details please see Ajv documentation.

NoSchemaError

NoSchemaError will be thrown when aev middleware is called but no schema is set.

NoSchemaForMethodError

aev throws NoSchemaForMethodError when its middleware is called but the provided schema file does not contain definitions for the request method.