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Most functional javascript object validation library


Sculp is a library that will help you cast and/or validate input data according to your schema. Typical applications include form management, validating object before saving to DB, casting HTTP request parameters to proper types, and many more.

Compared to other object validation libraries Sculp provides unique features such as conditional validation rules, incremental validation and object structure reuse.



  • Declarative schema. Schemas are simple objects, with a very easy-to-read structure. This means you can reuse them, clone them, extend them, and do with them whatever you want.
  • Support for custom types and validation rules. Any crazy rules you need. Array should be of odd length and its items should start with an underscore? No problem.
  • Conditional rules. Some field is present only if some checkbox field is on? No problem.
  • Fast incremental validation. You need to validate some gigantic form on the fly while user is editing it? Incremental validation ensures that only necessary fields and validation rules are recalculated.
  • Object structure reuse. To find out if your objects or validation rules have changed after last update by user, all you need is strict comparison. This makes this library very React-friendly.


$ npm install --save sculp


import { validate, Type, Presence } from 'sculp';
const schema = {
  type : Type.OBJECT,
  properties : {
    name : {
      type : Type.STRING,
      $lengthmin : 1
      $presence : Presence.REQUIRED
    gender : {
      type : Type.STRING_NET,
      transform : (v) => v && v.toLowerCase(),
      $values : [ 'male', 'female' ]
    age : {
      type : Type.NUMBER,
      $min : 0
    isAdult : {
      type : Type.BOOLEAN,
      compute : (fieldAccessor) =>
        fieldAccessor('^.age') >= 18
const result = validate({ name : 'John', gender : ' MALE ', age : '21' }, schema);
  // returns { name : 'John', gender : 'male', age : 21, isAdult : true } 
const result = validate({ age : -5 }, schema);
  // throws sculp.ValidationError with errors array 

This example schema defines the following constraints:

  • name property
    • should be string
    • should be not empty (minimum length is 1)
    • should be defined
  • gender property
    • should be string
    • will be trimmed and converted to lowercase
    • should be one of 2 values ("male", "female")
  • age property
    • should be not negative
  • isAdult property
    • boolean computed value

Schema structure

Schemas are plain javascript objects that can have following definition properties:


The type of a value. Should be string value. If type is not defined is defaults to Type.ANY_VALUE. There are 11 available types and you can define your own new types through defining custom casts. Predefined types available under Type enumeration:

import { Type } from 'sculp';

List of available types:

  • Type.STRING String type.
  • Type.STRING_NET String-not-empty-and-trimmed type. The same as Type.STRING but value gets trimmed and removed if it is an empty string.
  • Type.NUMBER Number type.
  • Type.BOOLEAN Boolean type.
  • Type.FUNCTION Function type.
  • Type.DATE Date type.
  • Type.OBJECT Object type. For this type you need to provide schemas for all properties using properties field.
  • Type.GROUP The same as Type.OBJECT but this type represents an object as just a group of fields and not as some entity. The difference is the validation of properties for undefined values. For Type.GROUP properties are validated and for Type.OBJECT they are not.
  • Type.ARRAY Array type. For this type you need to provide schema for array item using items field.
  • Type.ANY_VALUE Value of any type.
  • Type.ANY_OBJECT Object with any properties. No properties field needed.


The name of a value/field. Should be string or function returning string.


Any additional information that you want to attach to this value/field.


Can be defined for Type.NUMBER. Truncates the value to specified precision.


If any validation (other than type validation) fails on this field, value will be replaced by valid value if it is defined.


Provide initial value. You can get initial value for whole schema with getInitial(schema) function.


Used for Type.ARRAY, Type.OBJECT and Type.GROUP only. Overrides removeEmpty option for this value/field. If removeEmpty is true empty objects and arrays are removed. Default value is false.


Used for Type.OBJECT and Type.GROUP only. The value should be an object that provides schemas for available properties in the form of { prop1 : prop1Schema, prop2 : prop2Schema, ... }.


Used for Type.ARRAY only. The value should be a schema for array items.


A function or array of functions to transform value (e.g. convert string to lowercase). Those functions take current value as an argument and should return transformed value.


A function of array of functions to compute value (e.g. set object field value to some value derived on the values of other fields). Those functions take field accessor function as an argument and should return computed value.

$... validation rule properties

All schema properties that start with $ are validation rules. There are several predefined validations, and you can provide your custom validations using options or defining $custom validation. Any validation rule expects some rule value that value will be validated against. For example for $values rule value is expected to be an array of possible values ({ $values : [ 1, 2, 3 ] }). The value $... property should be a rule value or a function computing rule value.


const schema = {
  type : Type.OBJECT,
  properties : {
    string : {  
      type : Type.STRING,
      $lengthmin : 5,
      $presence : {
        value : Presence.REQUIRED,
        message : '"String" property is required!'
    longerString : {
      type : Type.STRING,
      $lengthmin : (fa) => {
        const stringPropValue = fa('^.string') || '';
        return stringPropValue.length + 1;

Available validations:

  • $presence Validates value presence. Available rule values are Presence.REQUIRED, Presence.OPTIONAL and Presence.ABSENT.
  • $values Validates that value is one of provided values. Rule value should be an array.
  • $regexp Validates that value matches regular expression. Rule value should be a string or RegExp.
  • $length Validates length of a value. Can be used for strings and arrays. Rule value is a number for exact length or an object with min and/or max properties for providing min and max limits (e.g. $length : { min : 1, max : 10 }).
  • $lengthmin Validates that value.length >= rule value. Can be used for strings and arrays.
  • $lengthmax Validates that value.length <= rule value. Can be used for strings and arrays.
  • $ne Validates that value !== rule value.
  • $min Validates that number value >= rule value.
  • $max Validates that number value <= rule value.
  • $gt Validates that number value > rule value.
  • $lt Validates that number value < rule value.

$custom custom validation rule

The $custom property value should be a function that returns error message string when validation fails and undefined otherwise. Function takes field accessor function as a first argument.


const schema = {
  type : Type.STRING,
  $custom : (fa) => {
    const value = fa() || '';
    return value[0] == 'A' ? undefined : 'String should start with an A letter'


Static functions


validate(value: any, schema: object, ?options: object): any

Validates value with schema and returns validated value or throws ValidationError when validation fails. Takes options as an optional argument.


validate('valid str', { type : Type.STRING, $length : 9 }, { strict : true });
  // returns string 'valid str' 
validate('invalid str', { type : Type.STRING, $length : 9 }, { strict : true });
  // throws ValidationError 


tryValidate(value: any, schema: object, ?options: object): object

Not throwing version of validate. Validates value with schema and returns object with result, errors and fieldsState fields. Takes options as an optional argument.

getSchemaValue(), getFieldName(), getFieldPresence()

getSchemaValue(value: any, schema: object, path: string, property: string): any
getFieldName(value: any, schema: object, path: string): string
getFieldPresence(value: any, schema: object, path: string): string

TODO : write description The use of this functions is discouraged.


getInitial(schema: object): any

Get initial value for schema. Constructed from initial property values of schema.


getSubSchema(schema: object, path: string): object

Get sub-schema for schema.


getSubSchema(schema, '.some.nested.field'); // returns schema for subfield 'some.nested.field' 


setDefaultOptions(options: object): undefined

Sets application-wide default options for validate and tryValidate methods as well as Sculp constructor.


  strict : true,
  casts : { ... },
  messages : russianLangMessages

Sculp class


Sculp(value: any, schema: object, ?options: object): undefined

Constructs new Sculp instance. Sculp instance allows you to perform fast incremental validations on your value when it changes. Takes options as an optional argument.


const value = { ... };
const sculp =  new Sculp(value, schema);
sculp.validate(); // returns validation result for value 
sculp.setField('.some.deep.nested.field', newValue); // mutates some field of value object 
sculp.validate(); // returns validation result for current value 


Sculp.prototype.validate(): any

The same as static validate but runs validation on current value using schema and options provided to Sculp constructor. Returns validated value or throws ValidationError when validation fails.


const sculp =  new Sculp({ field : 1 }, schema);
sculp.setField('.field', 2); // mutates field of value object 
sculp.validate(); // returns validation result for current value 


Sculp.prototype.tryValidate(): object

The same as static tryValidate but runs validation on current value using schema and options provided to Sculp constructor. Returns object with result, errors and fieldsState fields.


const sculp =  new Sculp({ field : 1 }, schema);
sculp.setField('.field', 2); // mutates field of value object 
sculp.tryValidate(); // returns object with validation result and errors 


Sculp.prototype.getValue(): any

Returns current value.


const sculp =  new Sculp({ field : 1 }, schema);
sculp.setField('.field', 2);
sculp.getValue(); // returns { field : 2 } 


Sculp.prototype.setValue(newValue: any): undefined

Replaces current value and clears all internal Sculp instance caches.


const sculp =  new Sculp({ field : 1 }, schema);
sculp.validate(); // returns validation result for { field : 1 } 
sculp.setValue({ newField : 2 }); // replaces 
sculp.validate(); // returns validation result for { newField : 2 } 

setField(), setFields()

Sculp.prototype.setField(path: string, value: any): undefined
Sculp.prototype.setFields(values: object): undefined

Mutates current value according to provided parameters. setField mutates one field, setFields can mutate several fields at once. Note that path parameter and values keys for mutating fields must start with a dot (i.e. '.field' and { '.field' : newValue }).


const sculp =  new Sculp({ list : [ {} ] }, schema);
sculp.setField('.list[0].a', 1);
sculp.setFields({ '.list[0].b' : 2, '.list[0].c' : 3 });
sculp.getValue(); // returns { list : [ { a : 1, b : 2, c : 3 } ] } 


Sculp.prototype.getFieldState(path: string): object

Returns field state object for path path of current value. See Field state object.

getSchemaValue(), getFieldName(), getFieldPresence()

Sculp.prototype.getSchemaValue(path: string, property: string): any
Sculp.prototype.getFieldName(path: string): string
Sculp.prototype.getFieldPresence(path: string): string

When you need to get value of some schema definition property or validation rule you can use getSchemaValue method. Useful to get values of conditional rules. For example, if you have conditional $presence rule for some field you can get current presence with getSchemaValue(path, '$presence').


const sculp =  new Sculp(value, schema);
sculp.getSchemaValue('.someField', '$values');
sculp.getFieldName('.someField'); // the same as sculp.getSchemaValue('.someField', 'name'); 
sculp.getFieldPresence('.someField'); // the same as sculp.getSchemaValue('.someField', '$presence'); 

Field Accessor Functions

Field accessor is a function that is passed to rule value functions and compute functions. Field accessor allows you to access other field values.

Field accessor usage:

fieldAccessor(); // returns value of current field 
fieldAccessor('.prop'); // returns field 'prop' of current field 
fieldAccessor('^.prop'); // returns field 'prop' of parent value 
fieldAccessor('^^.prop'); // returns field 'prop' of root value 


const schema = {
  type : Type.OBJECT,
  properties : {
    a : { type : Type.STRING },
    b : {
      type : Type.OBJECT,
      properties : {
        c : {
          compute : (fa) => 'prefix' + fa() // returns value of this field            
        d : {
          compute : (fa) => fa('^^.a') // returns field 'a'            
        e : {
          compute : (fa) => fa('^.c') // returns field 'b.c'            


These options can be provided to validate, tryValidate static functions and Sculp constructor. If you need to set options application-wide use setDefaultOptions function.


For i18n purposes you can provide your custom strings to use as error messages. Only English and Russian message strings are provided with the library right now. Default value is an object with English language error messages.


import russianMessages from 'sculp/lib/i18n/ru';
validate(value, schema, { messages : ruMessages });
// or
setDefaultOptions({ messages : ruMessages });


By default Sculp will try to cast value to required type. For example it will return 42 when validating string '42' with { type : Type.NUMBER } schema. If you don't want Sculp to try to cast values to required types you can set strict option to true. Default value is false.

casts and castsStrict

Option for providing casts for custom types. See Custom types and validations.


Option for providing custom validations. See Custom types and validations.

Custom types and validations

Custom types are provided with casts and castsStrict options. You should provide a cast function for each custom type. If value is not of your custom type your cast function should return special CAST_ERROR value. casts option is used for strict = false (default value) validations and castsStrict is used when strict = true.

Custom validations are provided with validations option. Validation function takes field accessor as first argument and validation rule value as second. Validation function should return error message string when validation fails and undefined otherwise.


import { validate } from 'sculp';
import { CAST_ERROR } from 'sculp/lib/enums';
const options = {
  casts : {
    'INTEGER' : (v) => {
      if (isNumber(v) && v === Math.round(v))
        return v;
      return CAST_ERROR;
  validations : {
    'divisible' : (fa, ruleValue) => {
      if (value && value % ruleValue !== 0)
        return `value is not divisible by ${ruleValue}`;
const schema = {
  type : 'INTEGER',
  $divisible : 3
validate(9, schema, options);

Field state object

TODO: document.


  • Partial validation support
  • Computed schemas support
  • Passing context
  • Add popular validation rules


MIT © dettier