validate-declarative

A simple utility for declaratively validating any Javascript object.

• Easy-to-read, self-describing syntax
• Fast, robust, and highly extensible
• Works with arbitrarily large and deeply nested objects/arrays
• ES5+ and browser compatible

See it in action:

import {verify, string, optionalNumber, boolean} from 'validate-declarative';

const schema = {
  a: boolean,
  b: {
    c: optionalNumber,
    d: { $test: (object) => object < 40000 }
  },
  e: { $element: string }
};

let data1 = {
  a: true,
  b: {
    d: 39328.03
  },
  e: [ "apple", "orange" ]
};
let result1 = verify(schema, data1); 
// returns true: data1 satisfies the schema

let data2 = {
  b: {
    c: "ten dollars",
    d: 60000
  },
  e: [ "23", -609, "lemon" ]
};
let result2 = verify(schema, data2);
// returns false, since:
//    'a' is missing,
//    'b.c' is not a number,
//    'b.d' is not less than 40000
//    'e[1]' is not a string

Table of Contents

• Installation
• Overview
• Examples
• API
• Constraints
• Errors
• Built-in Types
• About

Installation

npm install validate-declarative --save

yarn add validate-declarative

Overview

A schema is a plain Javascript object that has some special properties. A schema describes the structure and type of some data in a declarative manner.

import {verify, validate} from 'validate-declarative';

// a schema that describes a tweet
const tweetSchema = {
  message: {
    $test: function(object) {
      return typeof object === 'string' && object.length <= 24;
    }
  }
};

Keys in the schema beginning with $ are constraints. Constraints define the rules for validating data. The most commonly used constraint is the $test constraint, which defines a type test- a function that takes an object and returns true if the object is valid, false otherwise.

Conceptually, tweetSchema describes an object with a property message that is a string with a length of 24 characters or less. For a given tweet to be valid, then, it must satisfy these constraints.

The following tweet is valid:

let myTweet1 = { message: "Hello world!" };

But these tweets are invalid:

 // 'message' is not a string, invalid!
let myTweet2 = {message: 5};

// 'message' is greater than 24 characters, invalid!
let myTweet3 = {message: "Lorem ipsum dolor sit amet, consectetur adipiscing." };

To validate data against a schema, use verify()- it takes a schema as its first argument, and the data as its second argument. It returns true if the data satisfies the schema.

let result1 = verify(tweetSchema, myTweet1); // true
let result2 = verify(tweetSchema, myTweet2); // false
let result3 = verify(tweetSchema, myTweet3); // false

validate() is similar to verify(), but returns a report object containing an array of errors describing any constraint violations:

console.log(validate(tweetSchema, tweet2));
// {
//    errors: [ { error: "InvalidValueError", key: "message", value: 5 } ] 
//    data: { message: 5 }  
//    schema: { message: { '$test': [Function: $test] }
// }

import {verify, validate} from 'validate-declarative';

const tweetSchema = {
  message: {
    $test: function(object) {
      return typeof object === 'string' && object.length <= 24;
    }
  }
};

let myTweet1 = { message: "Hello world!" };
let myTweet2 = {message: 5};
let myTweet3 = {message: "Lorem ipsum dolor sit amet, consectetur adipiscing." };

let result1 = verify(tweetSchema, myTweet1); // true
let result2 = verify(tweetSchema, myTweet2); // false
let result3 = verify(tweetSchema, myTweet3); // false

console.log(validate(tweetSchema, tweet2));

This is a simple example, but schemas can be as large and complex as you want. You can create a schema for any Javascript object.

Check out more examples below, or learn about the other types of constraints. See the API for a detailed explanation of verify() and validate(). Also check out a list of the available built-in types.

Examples

This section contains some examples of common use cases.

import {verify, int, string} from 'validate-declarative';

let result1 = verify(int, 5);                 // true
let result2 = verify(int, "hello world");     // false
let result3 = verify(string, "hello world");  // true

import {verify, string, nonNegativeInt} from 'validate-declarative';

const courseSchema = {
  courseName: {
    $test: /^[A-Za-z0-9 ]+$/
  },
  roomCapacity: nonNegativeInt,
  professor: string
};

let objectOrientedCourse = {
  courseName: "Object Oriented Programming",
  roomCapacity: 30,
  professor: "Dr. Placeholder"
};

let result1 = verify(courseSchema, objectOrientedCourse); // true

import {verify, string} from 'validate-declarative';

const sedanSchema = {
  wheels: 4,
  model: string
};

let car1 = {
  wheels: 4,
  model: "Chrysler 300"
};

let car2 = {
  wheels: 5,
  model: "Chevrolet Impala"
};

let result1 = verify(sedanSchema, car1); // true
let result2 = verify(sedanSchema, car2); // false

import {verify, int} from 'validate-declarative';

// a custom type defining a prime number
const primeNumber = {
  $type: int,
  $test: function(object) {
    for(let i = 2; i < object; i++) {
      if(object % i === 0) {
        return false;
      }
    }
    return object !== 1 && object !== 0;
  },
  $name: 'primeNumber' // optional; defines the expectedType in error objects
};

let result1 = verify(primeNumber, 7); // true
let result2 = verify(primeNumber, 20); // false

import {string, verify} from 'validate-declarative';
import luhn from 'luhn-alg';

// a custom type defining a valid credit card number
const creditCardNumber = {
  $type: string,
  $test: function(object) {
    return luhn(object);
  },
  $name: "creditCardNumber",
};

// using a custom type in another schema
const purchaserSchema = {
  name: string,
  creditCardNumber: creditCardNumber,
};

let purchaser1 = {
  name: "John James",
  creditCardNumber: "4102676136588700",
};
let purchaser2 = {
  name: "Herbert Hubert",
  creditCardNumber: "4102676136588709",
};

let result1 = verify(purchaserSchema, purchaser1); // true
let result2 = verify(purchaserSchema, purchaser2); // false

import {verify, boolean} from 'validate-declarative';

// defines an array where each element is a boolean
const schema = {
  $element: boolean
};

let data1 = [true, true, false, true, false];
let data2 = [];
let data3 = [true, false, 3];

let result1 = verify(schema, data1); // true
let result2 = verify(schema, data2); // true
let result3 = verify(schema, data3); // false

import {verify} from 'validate-declarative';

// defines an array with at least 2 elements, and where each element has no leading/trailing whitespace
const schema = {
  $test: object => object.length > 1,
  $element: {
    $test: function(object) {
      return typeof object === 'string' && object.trim() === object;
    }
  }
};

let data1 = ["hello", "world"];
let data2 = ["hello", 2];
let data3 = ["hello"];
let data4 = ["  hello ", "world"];

let result1 = verify(schema, data1); // true
let result2 = verify(schema, data2); // false
let result3 = verify(schema, data3); // false
let result4 = verify(schema, data4); // false

import {verify, int} from 'validate-declarative';

// defines a 3 dimensional array of integers
const schema = {
  voxels: {
    $element: {
      $element: {
        $element: int
      }
    }
  }
};

let data = {
  voxels: [
    [[123, 48, 20], [93, 184, 230]],
    [[101, 200, 228], [76, 134, 120]],
    [[4, 67, 77], [129, 166, 249]]
  ]
};

let result = verify(schema, data); // true

import {verify, string, int} from 'validate-declarative';

const companySchema = {
  companyName: string,
  ceo: string,
  employees: {
    $element: {
      name: string,
      salary: int,
      beneficiaries: {
        $optional: true,
        $element: {
          name: string,
          relationship: string
        }
      }
    }
  }
};

let industryTech = {
  companyName: "Industry Tech, Inc.",
  ceo: "James Tech",
  employees: [
    {
      name: "John Q. Workingman",
      salary: 65000,
      beneficiaries: [
        {
          name: "Nancy Workingman",
          relationship: "Mother"
        },
        {
          name: "Bob Workingman",
          relationship: "Father"
        }
      ]
    },
    {
      name: "Fred T. Orphan",
      salary: 38000
    }
  ]
};

let result = verify(companySchema, industryTech); // true

import {verify, string} from 'validate-declarative';

const APIrequestSchema = {
  url: string,  
  params: {
    $type: string,
    $optional: true  
  }  
};

let request1 = {
  url: "video/watch/",
  params: "id=29340285723"
};

let request2 = {
  url: "video/list"
};

let result1 = verify(APIrequestSchema, request1); // true
let result2 = verify(APIrequestSchema, request2); // true

import {verify, string, positiveInt} from 'validate-declarative';

const productSchema = {
  productId: {
    $type: positiveInt,
    $unique: true
  },
  productName: string
};

let product1 = {
  productId: 1,
  productName: "Reclaimed Wood Desk"
};

let product2 = {
  productId: 1,
  productName: "Teak Writing Desk"
};

let result1 = verify(productSchema, product1); // true
let result2 = verify(productSchema, product2); // false

import {verify, string} from 'validate-declarative';

const playersSchema = {
  $element: {
    $type: string,
    $unique: true  
  }
};

let roster1 = ["Thomas", "James", "John"];
let roster2 = ["Linda", "Mary", "Mary"];

let result1 = verify(playersSchema, roster1); // true
let result2 = verify(playersSchema, roster2); // false

API

verify(schema, data, options={}) → boolean

Validates data (any Javascript object) against the schema (a constant, non-circular, plain object), returning true if and only if every property in the schema exists in the data, and every property's value in the data satisfies the constraints of the property (see Constraints), false otherwise. Prototypal properties in data are ignored. Uses Node's assert.deepStrictEqual() rules when comparing objects.

options is an optional argument that is an object with the following keys:

import {verify, int} from 'validate-declarative';

const schema = {
    a: int
};

let data = {
    a: 5
};

let options = {
    allowExtraneous: true,
    throwOnError: false
};

let result = verify(schema, data, options);

validate(schema, data, options={}) → Object

Same as verify(), but returns a report object containing a reference to the schema (schema), a reference to the data that was validated (data), and an array error objects (errors, see Errors) describing each constraint failure in detail. If the data satisfies the schema, errors will be an empty array, otherwise it will be non-empty.

setGlobalValidationOptions(options)

Sets the global validation rules for all validations. options is an optional argument that is an object with the following keys:

To restore the default global configuration, call setGlobalValidationOptions() with no arguments.

import {setGlobalValidationOptions} from 'validate-declarative';

let options = {
    allowExtraneous: false,
    throwOnError: true
};

setGlobalValidationOptions(options);

typeWithInstanceOf(clazz, name=clazz.name) → Object

Convenience function. Returns a type (an object with a $test constraint) that returns true if the object is not null and the object is an instanceof clazz, false otherwise. If name is present, it becomes the $name of the resulting type- otherwise the $name of the resulting type is set to clazz.name.

import {verify, typeWithInstanceOf} from 'validate-declarative';

class Apple {
    constructor() {}
}

const appleType = typeWithInstanceOf(Apple);

let data1 = new Apple();
let data2 = new Date();

let result1 = verify(appleType, data1); // true
let result2 = verify(appleType, data2); // false

_resetSchema(schema)

Resets the internal unique values within the schema, which are used to enforce uniqueness of values within and across data. Invoking this function is not recommended for normal use. After this function is invoked, uniqueness is no longer guaranteed on the schema.

import {verify, _resetSchema, int} from 'validate-declarative';

const schema = {
    $type: int,
    $unique: true
};

let result1 = verify(schema, 5); // true
let result2 = verify(schema, 5); // false
_resetSchema(schema);
let result3 = verify(schema, 5); // true

Constraints

Constraints define the rules for validating data. They are embedded in schema objects alongside ordinary properties. Constraints begin with $ to differentiate them from ordinary properties. There are five types of constraints: $test, $type, $optional, $unique, and $element.

$test

Default: (object) => true

Defines a simple type test. $test is a function that takes an object and returns true if the object is valid, false otherwise. By default, the object is always valid. Alternatively, $test is a regular expression that describes a valid object. If the object is invalid, an InvalidValueError is generated.

(Note: $test does not perform any Javascript Error handling. Calling a function like charAt() on an object without first checking that it is a string will throw a Javascript Error if the object is not a string.)

// a custom type
const countryCode = {
  $test: function(object) {
    // a valid country code is a string with 3 characters
    return typeof object === 'string' && object.length === 3;
  }
};

// using the type in a schema
const countrySchema = {
  country: countryCode
};

let country1 = {
  country: "USA"
};

let country2 = {
  country: "Brazil"
};

let result1 = verify(countrySchema, country1); // true
let result2 = verify(countrySchema, country2); // false, fails $test

// Using a regular expression instead of a function
const countryCode = {
  $test: /^[A-Za-z]{3}$/
};

const countrySchema = {
  country: countryCode
};

$type

Default: { $test: (object) => true }

Allows you to extend an existing type. $type is any object with a $test property that is a type test (see above). There can be many $type declarations nested within each other. During validation, the deepest $test is called first, then the second-deepest, and so on. This functionality allows you to easily 'chain' series of type tests together to create original custom types (see example #2 below). Indeed, many of the built-in types included in this package are defined this way (number 🡒 int 🡒 positiveInt).

If neither $test nor $type is present, the validated object is always valid.

You can add a $name property to your custom type, which determines the expectedType in a generated error- though this is entirely optional.

import {nonNegativeInt} from 'validate-declarative';

// palindrome extends nonNegativeInt
const palindrome = {
  // nonNegativeInt is an object with its own $test
  $type: nonNegativeInt,
  $test: function(object) {
    let str = object + "";
    return str === str.split("").reverse().join("");
  },
  $name: 'palindrome' // optional
};

const schema = {
  streetNumber: palindrome
};

// A type may contain many deeply nested $tests
// The deepest $test is always called first
const array = {
  $test: function(object) { // called first
    return Array.isArray(object);
  }
};

// smallArray extends array
const smallArray = {
  $type: array,
  $test: function(object) { // called second
    return object.length < 5;
  }
};

// smallNoDuplicatesArray extends smallArray
const smallNoDuplicatesArray = {
  $type: smallArray,
  $test: function(object) { // called third
    return (new Set(object)).size === object.length;
  }
};

const schema = {
  cars: smallNoDuplicatesArray
};

$optional

Default: false

Declares a property optional. By default, all properties in the schema are required. If $optional is true, a MissingPropertyError will not be generated if the property does not exist in the data. For nested $optional declarations, only the most shallow $optional declaration is considered. $optional declarations at the top level of the schema or at the top level of an $element object are ignored.

import {verify, int, string} from 'validate-declarative';

const schema = {
  foo: int,
  bar: {
    $type: string,
    $optional: true
  }
};

let data1 = {
  foo: -100,
  bar: "hello world"
};

let data2 = {
  foo: 5
};

let result1 = verify(schema, data1); // true
let result2 = verify(schema, data2); // true

$unique

Default: false

Declares a value of a property or an array element to be unique across all data validated against a particular schema. By default, all properties in a schema are non-unique. If $unique is true, the property will generate a DuplicateValueError when a duplicate value is detected across two data or detected within the same data (ex. duplicate values in an array). For nested $unique declarations, only the most shallow $unique declaration is considered.

(Note: Every NaN value is different from every other value, including other NaN values (as per the ECMAScript spec). It would therefore be meaningless to declare a NaN property unique- as it will always be unique.)

(Note: Each $unique declaration is mapped to an internal array of values stored within a hidden property within the schema. Be warned- a large number of validations may result in high memory usage, as every validation adds another element to each internal array of unique values within the schema. Though it is not recommended for normal use, you can call _resetSchema() to clear these internal arrays (see API). This, however, will not guarantee uniqueness for subsequent validations.)

import {verify, string} from 'validate-declarative';

const playerSchema = {
  username: {
    $type: string,
    $unique: true
  },
  password: string
};

let player1 = {
  username: "Mariosunny",
  password: "123abc"
};

let player2 = {
  username: "Mariosunny",
  password: "password1"
};

// true
let result1 = verify(playerSchema, player1);

// false - there is already a player with username "Mariosunny"
let result2 = verify(playerSchema, player2);

$element

Default: undefined

Defines the schema of each element in an array or set. When $element is present, $type defaults to the list type (see Built-in Types). $element declarations can be nested within eachother to validate multi-dimensional arrays.

import {verify, string, number} from 'validate-declarative';

const restaurantSchema = {
  headChef: string,
  menuItems: {
    $element: {
      name: string,
      price: number
    }
  }
};

let restaurant1 = {
  headChef: "Emeril Ramsay",
  menuItems: [
    {
      name: "Cheeze Pizza",
      price: 12.99
    },
    {
      name: "Beef Stew",
      price: 7.50
    }
  ]
};

let result = verify(restaurantSchema, restaurant1); // true

Errors

This section contains a comprehensive list of errors that could be generated by validate(). An error is an object that is generated when an object in the data fails a constraint in the schema.

(Note that, despite the name, the process of error generation in this context does not refer to error throwing)

InvalidValueError

Generated when a value fails a type test.

{
  error: "InvalidValueError",    // the type of error that occurred
  key: "menu.menuItems[3].desc", // the property where the error occurred
  value: 5,                      // the actual value found in the data at the property
  expectedType: "string"         // the expected type, defined by $name
}

DuplicateValueError

Generated when $unique = true and a duplicate value is detected within/across the data.

{
  error: "DuplicateValueError",
  key: "candidates[2].SSN",
  value: "123-45-6789"
}

MissingPropertyError

Generated when $optional = false and a property is missing from the data.

{
  error: "MissingPropertyError",
  key: "company.shippingAddress"
}

ExtraneousPropertyError

Generated when allowExtraneous = false and there is an extra property in the data.

{
  error: "ExtraneousPropertyError",
  key: "favoriteColor"
}

Built-in Types

This section contains a list of the built-in types that are included in this package. See the examples for how to use types or how to define your own type.

Core Types

Optional types

Optional types are the same as core types, but with $optional = true.

Unique types

Unique types are the same as core types, but with $unique = true.

About

This project is maintained by Tyler Hurson. Submit any issues or pull requests to the official Github repo.

Check out other projects by this author:

• unravel-function - Takes a function and spreads its arguments across a chain of functions to be lazily evaluated.