🚀 Express-validator

A lightweight custom validator for Express.js that supports:

• ✅ Simple rules
• ✅ Stops at the first error per field
• ✅ Works with MongoDB or MySQL
• ✅ Async database checks

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📦 Installation

npm install @arweb/express-validate-rules

Validation Rules Reference

Below is the list of all supported validation rules with their usage format and behavior.

Rule	Database	Gives error when...	Use
required	❌ No	Value is null or empty	{ validator: "required", message: "Your message" }
required_if	❌ No	Field is empty when another field has a specific value	{ validator: "required_if", message: "Your message", options: { other: "field_name", val: "any / or not needed" } }
email	❌ No	Value is not a valid email	{ validator: "email", message: "Your message" }
url	❌ No	Value is not a valid URL	{ validator: "url", message: "Your message" }
alpha	❌ No	Value contains non-alphabetic characters	{ validator: "alpha", message: "Your message" }
alphanumeric	❌ No	Value contains characters other than letters or numbers	{ validator: "alphanumeric", message: "Your message" }
no_spaces	❌ No	Value contains spaces	{ validator: "no_spaces", message: "Your message" }
no_special_chars	❌ No	Value contains special characters	{ validator: "no_special_chars", message: "Your message" }
equal	❌ No	Value does not equal provided string	{ validator: "equal", message: "Your message", options: { allow: "Some Text" } }
not_equal	❌ No	Value equals the disallowed string	{ validator: "not_equal", message: "Your message", options: { disallow: "Some Text" } }
uuid	❌ No	Value is not a valid UUID (v1–v8 or any)	{ validator: "uuid", message: "Your message", options: { type: "any" } }
slug	❌ No	Value is not a valid slug	{ validator: "slug", message: "Your message" }
regex	❌ No	Value does not match the pattern	{ validator: "regex", message: "Your message", options: { pattern: "Pattern", flags: "Flags" } }
contain	❌ No	Value does not contain given element	{ validator: "contain", message: "Your message", options: { element: "Some text or array" } }
not_contain	❌ No	Value contains disallowed element	{ validator: "not_contain", message: "Your message", options: { element: "Some text or array" } }
string_case	❌ No	Value is not in the required case (lower/upper/title)	{ validator: "string_case", message: "Your message", options: { case_type: "lower" } }
string_length	❌ No	String length does not meet criteria (min/max/exact)	{ validator: "string_length", message: "Your message", options: { length: 3, length_type: "min" } }
starts_with	❌ No	Value does not start with given prefix	{ validator: "starts_with", message: "Your message", options: { prefix: "Some Text" } }
ends_with	❌ No	Value does not end with given suffix	{ validator: "ends_with", message: "Your message", options: { suffix: "Some Text" } }
ascii	❌ No	Value is not valid ASCII	{ validator: "ascii", message: "Your message" }
json	❌ No	Value is not valid JSON	{ validator: "json", message: "Your message" }
array	❌ No	Value is not a valid array	{ validator: "array", message: "Your message" }
gt	❌ No	Value is ≤ provided val	{ validator: "gt", message: "Your message", options: { val: 3 } }
gte	❌ No	Value is < provided val	{ validator: "gte", message: "Your message", options: { val: 3 } }
lt	❌ No	Value is ≥ provided val	{ validator: "lt", message: "Your message", options: { val: 3 } }
lte	❌ No	Value is > provided val	{ validator: "lte", message: "Your message", options: { val: 3 } }
number_between	❌ No	Value is not between min and max	{ validator: "number_between", message: "Your message", options: { min: 5, max: 9 } }
integer	❌ No	Value is not an integer	{ validator: "integer", message: "Your message" }
positive	❌ No	Value is not positive	{ validator: "positive", message: "Your message" }
negative	❌ No	Value is not negative	{ validator: "negative", message: "Your message" }
float	❌ No	Value is not float/double	{ validator: "float", message: "Your message" }
numeric	❌ No	Value is not numeric	{ validator: "numeric", message: "Your message" }
even	❌ No	Value is not even	{ validator: "even", message: "Your message" }
odd	❌ No	Value is not odd	{ validator: "odd", message: "Your message" }
boolean	❌ No	Value is not a valid boolean	{ validator: "boolean", message: "Your message" }
is_true	❌ No	Value is not true	{ validator: "is_true", message: "Your message" }
is_false	❌ No	Value is not false	{ validator: "is_false", message: "Your message" }
file_required	❌ No	File is missing or empty	{ validator: "file_required", message: "Your message" }
file_mime	❌ No	File MIME type does not match	{ validator: "file_mime", message: "Your message", options: { types: ["image/jpeg", "image/png"] } }
file_storage_size	❌ No	File size does not match rule (min/max/exact)	{ validator: "file_storage_size", message: "Your message", options: { size_bytes: 100000, size_type: "max/min/exact" } }
file_extension	❌ No	File extension does not match allowed list	{ validator: "file_extension", message: "Your message", options: { extension: [".jpg", ".png"] } }
image_dimensions	❌ No	Image dimensions are invalid	{ validator: "image_dimensions", message: "Your message", options: { width: 200, height: 100, width_type: "max/min/exact", height_type: "max/min/exact" } }
exists	✅ Yes	Value does not exist in the specified database collection	{ validator: "exists", message: "Your message", options: { collection: "users", field: "email", exclude: [{ field: "id", value: req.params.id, logic: "AND" }] } } Ensures the value already exists (useful for foreign key or reference checks).
unique	✅ Yes	Value already exists (not unique) in the specified database collection	{ validator: "unique", message: "Your message", options: { collection: "users", conditions: [{ field: "username", value: req.body.username, logic: "AND" }, { field: "email", value: req.body.email, logic: "OR" }], exclude: [{ field: "id", value: req.params.id, logic: "AND" }] } } Ensures values are unique across one or more fields. Supports logical operators (AND / OR) and multiple exclusions.
not_exists	✅ Yes	Value already exists in the specified database collection	{ validator: "not_exists", message: "Your message", options: { collection: "users", field: "email", exclude: [{ field: "id", value: req.params.id, logic: "AND" }] } } Ensures the value does not exist before inserting or updating. Commonly used for uniqueness checks during creation.

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🧠 Summary

Rule	Validation Logic
exists	Must already exist in DB
unique	Must be unique (not duplicated) in DB
not_exists	Must not exist in DB at all

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✅ Notes:

• exclude supports an array of conditions with individual logic values.
• Default logic between conditions is AND if not specified.
• These database validations can be combined with non-database ones in the same validation set.

Issues

Facing bugs, please raise a Issue