fastest-validator

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:zap: The fastest JS validator library for NodeJS

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:zap: The fastest JS validator library for NodeJS

fastest-validator

:zap: The fastest JS validator library for NodeJS | Browser | Deno.

Key features

blazing fast! Really!
24 built-in validators
many sanitizations
custom validators & aliases
nested objects & array handling
strict object validation
multiple validators
customizable error messages
programmable error object
no dependencies
unit tests & 100% coverage

How fast?

Very fast! 8 million validations/sec (on Intel i7-4770K, Node.JS: 12.14.1)

√ validate                            8,678,752 rps

Compared to other popular libraries:

50x faster than Joi.

Would you like to test it?

$ git clone https://github.com/icebob/fastest-validator.git
$ cd fastest-validator
$ npm install
$ npm run bench

Approach

In order to achieve lowest cost/highest performance redaction fastest-validator creates and compiles functions using the Function constructor. It's important to distinguish this from the dangers of a runtime eval, no user input is involved in creating the validation schema that compiles into the function. This is as safe as writing code normally and having it compiled by V8 in the usual way.

Installation

NPM

You can install it via NPM.

$ npm i fastest-validator --save

$ yarn add fastest-validator

Usage

Validate

The first step is to compile the schema to a compiled "checker" function. After that, to validate your object, just call this "checker" function.

This method is the fastest.

…

Try it on Repl.it

Halting

If you want to halt immediately after the first error:

javascript

const v = new Validator({ haltOnFirstError: true });

Browser usage

xml

<script src="https://unpkg.com/fastest-validator"></script>

javascript

const v = new FastestValidator();

const schema = {
    id: { type: "number", positive: true, integer: true },
    name: { type: "string", min: 3, max: 255 },
    status: "boolean" // short-hand def
};

const check = v.compile(schema);

console.log(check({ id: 5, name: "John", status: true }));
// Returns: true

Deno usage

With esm.sh, now Typescript is supported

javascript

import FastestValidator from "https://esm.sh/fastest-validator@1"

const v = new FastestValidator();
const check = v.compile({
    name: "string",
    age: "number",
});

console.log(check({ name: "Erf", age: 18 })); //true

Supported frameworks

Moleculer: Natively supported
Fastify: By using fastify-fv
Express: By using fastest-express-validator

Optional, Required & Nullable fields

Optional

Every field in the schema will be required by default. If you'd like to define optional fields, set optional: true.

javascript

const schema = {
    name: { type: "string" }, // required
    age: { type: "number", optional: true }
}

const check = v.compile(schema);

check({ name: "John", age: 42 }); // Valid
check({ name: "John" }); // Valid
check({ age: 42 }); // Fail because name is required

Nullable

If you want disallow undefined value but allow null value, use nullable instead of optional.

javascript

const schema = {
    age: { type: "number", nullable: true }
}

const check = v.compile(schema);

check({ age: 42 }); // Valid
check({ age: null }); // Valid
check({ age: undefined }); // Fail because undefined is disallowed
check({}); // Fail because undefined is disallowed

Nullable and default values

null is a valid input for nullable fields that has default value.

javascript

const schema = {
   about: { type: "string", nullable: true, default: "Hi! I'm using javascript" }
}

const check = v.compile(schema)

const object1 = { about: undefined }
check(object1) // Valid
object1.about // is "Hi! I'm using javascript"

const object2 = { about: null }
check(object2) // valid
object2.about // is null

check({ about: "Custom" }) // Valid

Considering `null` as a value

In specific case, you may want to consider null as a valid input even for a required field.

It's useful in cases you want a field to be:

required and null without specifying nullable: true in its definition.
required and not null by specifying nullable: false in its definition.
optional but specifically not null.

To be able to achieve this you'll have to set the considerNullAsAValue validator option to true.

javascript

const v = new Validator({considerNullAsAValue: true});

const schema = {foo: {type: "number"}, bar: {type: "number", optional: true, nullable: false}, baz: {type: "number", nullable: false}};
const check = v.compile(schema);

const object1 = {foo: null, baz: 1};
check(object1); // valid (foo is required and can be null)

const object2 = {foo: 3, bar: null, baz: 1};
check(object2); // not valid (bar is optional but can't be null)

const object3 = {foo: 3, baz: null};
check(object3); // not valid (baz is required but can't be null)

With this option set all fields will be considered nullable by default.

Strict validation

Object properties which are not specified on the schema are ignored by default. If you set the $$strict option to true any additional properties will result in an strictObject error.

javascript

const schema = {
    name: { type: "string" }, // required
    $$strict: true // no additional properties allowed
}

const check = v.compile(schema);

check({ name: "John" }); // Valid
check({ name: "John", age: 42 }); // Fail

Remove additional fields

To remove the additional fields in the object, set $$strict: "remove".

Multiple validators

It is possible to define more validators for a field. In this case, only one validator needs to succeed for the field to be valid.

javascript

const schema = {
    cache: [
        { type: "string" },
        { type: "boolean" }
    ]
}

const check = v.compile(schema);

check({ cache: true }); // Valid
check({ cache: "redis://" }); // Valid
check({ cache: 150 }); // Fail

Root element schema

Basically the validator expects that you want to validate a Javascript object. If you want others, you can define the root level schema, as well. In this case set the $$root: true property.

Example to validate a string variable instead of object

javascript

const schema = {
    $$root: true,
    type: "string", 
    min: 3, 
    max: 6
};

const check = v.compile(schema);

check("John"); // Valid
check("Al"); // Fail, too short.

Sanitizations

The library contains several sanitizers. Please note, the sanitizers change the original checked object.

Default values

The most common sanitizer is the default property. With it, you can define a default value for all properties. If the property value is null* or undefined, the validator set the defined default value into the property.

Static Default value example:

javascript

const schema = {
    roles: { type: "array", items: "string", default: ["user"] },
    status: { type: "boolean", default: true },
};

const check = v.compile(schema);

const obj = {}

check(obj); // Valid
console.log(obj);
/*
{
    roles: ["user"],
    status: true
}
*/

Dynamic Default value: Also you can use dynamic default value by defining a function that returns a value. For example, in the following code, if createdAt field not defined in object`, the validator sets the current time into the property:

javascript

const schema = {
    createdAt: {
        type: "date",
        default: (schema, field, parent, context) => new Date()
    }
};

const check = v.compile(schema);

const obj = {}

check(obj); // Valid
console.log(obj);
/*
{
    createdAt: Date(2020-07-25T13:17:41.052Z)
}
*/

Shorthand definitions

You can use string-based shorthand validation definitions in the schema.

javascript

const schema = {
    password: "string|min:6",
    age: "number|optional|integer|positive|min:0|max:99", // additional properties
    state: ["boolean", "number|min:0|max:1"] // multiple types
}

Array of X

javascript

const schema = {
    foo: "string[]" // means array of string
}

const check = v.compile(schema);

check({ foo: ["bar"] }) // true

Nested objects

javascript

const schema = {
   dot: {
      $$type: "object",
      x: "number",  // object props here
      y: "number",  // object props here
   }, 
   circle: {
      $$type: "object|optional", // using other shorthands
      o: {
         $$type: "object",
         x: "number",
         y: "number",
      },
      r: "number"
   }
};

Alias definition

You can define custom aliases.

javascript

v.alias('username', {
    type: 'string',
    min: 4,
    max: 30
    // ...
});

const schema = {
    username: "username|max:100", // Using the 'username' alias
    password: "string|min:6",
}

Default options

You can set default rule options.

javascript

const v = new FastestValidator({
    defaults: {
        object: {
            strict: "remove"
        }
    }
});

Label Option

You can use label names in error messages instead of property names.

javascript

const schema = {
	email: { type: "email", label: "Email Address" },
};
const check = v.compile(schema);

console.log(check({ email: "notAnEmail" }));

/* Returns
[
  {
    type: 'email',
    message: "The 'Email Address' field must be a valid e-mail.",
    field: 'email',
    actual: 'notAnEmail',
    label: 'Email Address'
  }
]
*/

Built-in validators

`any`

This does not do type validation. Accepts any types.

javascript

const schema = {
    prop: { type: "any" }
}

const check = v.compile(schema)

check({ prop: true }); // Valid
check({ prop: 100 }); // Valid
check({ prop: "John" }); // Valid

`array`

This is an Array validator.

Simple example with strings:

javascript

const schema = {
    roles: { type: "array", items: "string" }
}
const check = v.compile(schema)

check({ roles: ["user"] }); // Valid
check({ roles: [] }); // Valid
check({ roles: "user" }); // Fail

Example with only positive numbers:

javascript

const schema = {
    list: { type: "array", min: 2, items: {
        type: "number", positive: true, integer: true
    } }
}
const check = v.compile(schema)

check({ list: [2, 4] }); // Valid
check({ list: [1, 5, 8] }); // Valid
check({ list: [1] }); // Fail (min 2 elements)
check({ list: [1, -7] }); // Fail (negative number)

Example with an object list:

javascript

const schema = {
    users: { type: "array", items: {
        type: "object", props: {
            id: { type: "number", positive: true },
            name: { type: "string", empty: false },
            status: "boolean"
        }
    } }
}
const check = v.compile(schema)

check({
    users: [
        { id: 1, name: "John", status: true },
        { id: 2, name: "Jane", status: true },
        { id: 3, name: "Bill", status: false }
    ]
}); // Valid

Example for enum:

javascript

const schema = {
    roles: { type: "array", items: "string", enum: [ "user", "admin" ] }
}

const check = v.compile(schema)

check({ roles: ["user"] }); // Valid
check({ roles: ["user", "admin"] }); // Valid
check({ roles: ["guest"] }); // Fail

Example for unique:

javascript

const schema = {
    roles: { type: "array", unique: true }
}
const check = v.compile(schema);

check({ roles: ["user"] }); // Valid
check({ roles: [{role:"user"},{role:"admin"},{role:"user"}] }); // Valid
check({ roles: ["user", "admin", "user"] }); // Fail
check({ roles: [1, 2, 1] }); // Fail

Example for convert:

javascript

const schema = {
    roles: { type: "array", items: 'string', convert: true }
}
const check = v.compile(schema);

check({ roles: ["user"] }); // Valid
check({ roles: "user" }); // Valid
// After both validation: roles = ["user"]

Pro

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PublishedAug 1, 2026

UpdatedSep 17, 2026

Category编程语言

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fastest-validator

About

fastest-validator

Key features

How fast?

Approach

Installation

NPM

Usage

Validate

Halting

Browser usage

Deno usage

Supported frameworks

Optional, Required & Nullable fields

Optional

Nullable

Nullable and default values

Considering null as a value

Strict validation

Remove additional fields

Multiple validators

Root element schema

Sanitizations

Default values

Shorthand definitions

Array of X

Nested objects

Alias definition

Default options

Label Option

Built-in validators

any

array

Pro

Issues· 45 open

> Tags

> Discussion

> Details

> Related tools

Considering `null` as a value

`any`

`array`