express-body-validation ✅

Lightweight Express middleware for validating req.body against a schema.

Install 📦

npm install @r01al/express-body-validation

Usage 🚀

import express from "express";
import { SchemaType, validateBody } from "@r01al/express-body-validation";

const app = express();
app.use(express.json());

app.post(
	"/users",
	validateBody({
		name: SchemaType.String,
		age: SchemaType.Number,
		address: {
			city: SchemaType.String
		},
		tags: [SchemaType.String],
		score: (value) => typeof value === "number" && value >= 0
	}),
	(req, res) => {
		res.json({ ok: true });
	}
);

API 📚

validateBody(schema)

Returns an Express middleware that validates req.body.

• schema: SchemaValue

SchemaType

Use these constants instead of raw strings:

• SchemaType.String
• SchemaType.Number
• SchemaType.Boolean
• SchemaType.Object
• SchemaType.Array
• SchemaType.Null
• SchemaType.Any

SchemaValue

import type { SchemaValue } from "@r01al/express-body-validation";

const schema: SchemaValue = {
	name: SchemaType.String,
	age: SchemaType.Number
};

Supported shapes:

• Primitives: SchemaType.*
• Objects: { user: { id: SchemaType.Number } }
• Arrays: [SchemaType.String] or [{ id: SchemaType.Number }]
• Functions: (value) => boolean to fully override validation at that node

Schema is validated before use. Invalid schemas return an error message instead of throwing.

Examples ✨

Array body

app.post(
	"/tags",
	validateBody([
		SchemaType.String
	]),
	(req, res) => {
		res.json({ ok: true });
	}
);

Nested object + arrays

validateBody({
	order: {
		id: SchemaType.String,
		items: [
			{
				sku: SchemaType.String,
				qty: SchemaType.Number
			}
		]
	}
});

Function override

validateBody({
	password: (value) => typeof value === "string" && value.length >= 8
});

Function validator details

• The function receives the raw value at that schema node.
• Return true to accept, false to reject.
• If the function throws, the error is caught and returned as a validation message.

Example with custom error message:

validateBody({
	age: (value) => {
		if (typeof value !== "number") {
			throw new Error("age must be a number");
		}
		return value >= 18;
	}
});

Errors ⚠️

If validation fails, the middleware responds with HTTP 400:

{ "message": "missing field 'payload.user.name'" }

or

{ "message": "invalid field 'payload.age': expected number, got string" }

Build 🛠️

npm run build

Test 🧪

npm test

Node Support 🟢

• Node >=14 (see package.json engines)

License 📝

ISC