validate()

Import

const { validate } = require('kaelum/validate');

This is a subpath export — it does not come from the main kaelum package. Import it explicitly only when needed.

Signature

validate(schema)

Parameters

Name	Type	Description
schema	Object	Validation schema. Accepts body, query, and/or params keys.
schema.body	Object	Rules for req.body fields.
schema.query	Object	Rules for req.query fields. Values are coerced before validation.
schema.params	Object	Rules for req.params fields. Values are coerced before validation.

Field Rules

Each key in a target object is a field name. Its value is a rules object:

Rule	Type	Description
type	'string' | 'number' | 'boolean' | 'array' | 'object'	Expected type
required	boolean	Field must be present and non-empty
min	number	String: min chars. Number: min value. Array: min items
max	number	String: max chars. Number: max value. Array: max items
pattern	string | RegExp	Preset name or custom RegExp (strings only)
custom	(value) => true | string	Custom function — return true to pass

Pattern Presets

Preset	Validates
'email'	user@domain.tld
'url'	http(s)://...
'uuid'	Standard UUID v4
'alphanumeric'	Letters and digits only

Returns

An Express RequestHandler (middleware function).

• On failure: Responds 400 with { error: "Validation failed", fields: [...] }. All field errors are collected before responding.
• On success: Calls next().

Examples

// Basic usage
validate({
  body: {
    name:  { type: 'string', required: true, min: 2 },
    email: { type: 'string', required: true, pattern: 'email' },
  },
});

// Validate query params with type coercion
validate({
  query: {
    page:  { type: 'number', min: 1 },
    limit: { type: 'number', max: 100 },
  },
});

// Custom validator
validate({
  body: {
    score: {
      type: 'number',
      custom: (v) => v % 2 === 0 || 'Score must be even',
    },
  },
});