json-schema-library: A TypeScript repository from benurb

Customizable and hackable json-validator and json-schema utilities for traversal, data generation and validation

This package offers tools and utilities to work with json-schema, create and validate data. Unfortunately, most packages, editors or validators do not care to expose basic json-schema functionality. Instead of small memory footprint or high performance, this package focuses on exposing utilities for browser and node environments and lessens the pain to build custom tools around json-schema.

npm i json-schema-library -S or yarn add json-schema-library

This package is tested on node v10.16 and in latest Browsers.
This library currently supports all draft4 features (@see benchmark)

Breaking Changes
Overview
1. Core
2. Add Custom Validators
Custom Extensions

Breaking Changes

with version v5.0.0 the apie has changed to es6 modules, where there is no default epxport, only named exports. Additionally all code has been rewritten to typescript. If directly accessing files, switch to dist/module/*.js-files for plain js-modules.
with version v4.0.0 the api has changed in order to use the defined (root) schema in core as default where possible. This means, most methods have a a changed signature, where data is passed before an optional schema argument. Check the Core Overview for the current signature
additionally iterateSchema has been renamed to eachSchema for consistency

Overview

Either select an existing validator (core) or create your own. Each Core holds all functions that are required for the json-schema operations like validation. In order to overwrite a custom function you can either

modify the map-objects (i.e. /lib/validation/keywords.js)
overwrite functions or keys in the generated instance (const instance = new Core())
Create a custom Core following the examples in /lib/cores

Additionally, helper functions and tools are separately exposed via CommonJS Modules. Most of them do require a core-object as parameter, but use only some of the functions defined in an core-instance.

Core

The default interface of a validator can be found in /lib/cores/CoreInterface. It exposes the following methods

method	signature	description
constructor	schema : instance	pass the root-schema in the constructor
each	data, callback, [schema], [pointer]	Iterates over the data, passing value and its schema
getSchema	pointer, [data], [schema] : Schema	Get the json-schema describing the `data` found at `pointer`
getTemplate	data, [schema] : Mixed	returns a template object based of the given json-schema
isValid	data, [schema], [pointer] : Boolean	Check if the given schema validates the data
resolveOneOf	data, [schema], [pointer] : Schema	returns the oneOf-schema for the passed data
resolveRef	schema : Schema	resolves a $ref on a given schema-object
setSchema	schema	set a new (root) schema
step	key, schema, data, [pointer] : Schema	step into a json-schema by the given key (property or index)
validate	data, [schema], [pointer] : Array	Get a list of validation errors

Each core holds some mapping objects, that may be modified

Core {
    // keyword validations for each type, e.g. "array": ["enum", "items", "minItems", "maxItems", ...]
    // for each item in the given list, the validation function in `validationKeyword` will be called
    typeKeywords: {} 
    // keyword validation functions, e.g. validateKeyword.enum(), validateKeyword.items(), ...
    validateKeyword: {}
    // type validation for array, object, number, etc. Basically runs over typeKeywords and executes
    // validation functions from `validateKeyword`
    validateType: {}
    // format validation functions. will be executed if a) typeKeywords includes 'format' and a
    // validation function is set in validateFormat
    validateFormat: {}
    // list of error-creator functions. They receive an object with the data of the error and must
    // return an object like { type: 'error', message: "" }
    errors: {}
}

Examples

getSchema(core, pointer, [data], [schema])

Get the json-schema describing the data found at pointer. The default json-schema-definitions can be resolved without any data as input: core.getSchema('#/article/title'). For any dynamic values (like oneOf, definitions) the data has to be passed in addition.

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
const targetSchema = core.getSchema('#/path/to/target', rootData);

Currently may also return an error:

if (targetSchema.type === "error") {
    throw new Error(targetSchema.message);
}

Or using getSchema directly

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
const targetSchema = getSchema(core, '#/path/to/target', rootData);

getTemplate(core, data, [schema])

Generate data which is valid to the given json-schema. Additionally, a data object may be given, which will be extended by any missing items or properties.

import { Draft04 as Core } from "json-schema-library";
const core = new Core();
const baseData = core.getTemplate(
    { other: true },
    { type: "object", properties: { target: { type: "string", default: "v" } } },
); // returns { other: true, target: "v" }

validate(core, data, [schema])

Get a list of validation errors

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
const errors = core.validate({ validationOf: "rootSchema" });
// validation errors running data for 'rootSchema'
const customSchemaErrors = core.validate("", { type: "number" });
// returns { type: "TypeError" }

isValid(core, data, [schema])

Check if the given schema validates the data

basically core.validate("", { type: "number" }).length === 0

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
const baseSchema = core.isValid("", { type: "number" });
// returns false

validateAsync(core, data, [options])

Asynchronous validation helper

Optional support for onError helper, which is invoked for each error (after being resolved)

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
// signature: Core, data, { onError: [onErrorCallback], schema: JSONSchema, pointer: [Pointer]} : Promise
validateAsync(core, "", { onError: (err) => {}, schema: { type: "number" } })
    .then(allErrors => {});

step(core, key, schema, data)

Get the json-schema of a child-property

import { Draft04 as Core } from "json-schema-library";
const core = new Core(rootSchema);
const baseSchema = core.step(   
    "target"
    { type: "object", properties: { target: { type: "string" } } },
    { target: "value" }
); // returns {type: "string"}

each(core, data, callback, [schema])

Iterates over each data-item (object, array and value); passing the value and its corresponding schema

import { Draft04 as Core } from "json-schema-library";
const core = new Core({
    type: "array",
    items: [
        { type: "number" },
        { type: "string" }
    ]
});
core.each([5, "nine"], (schema, value, pointer) => {
// 1. schema = { type: "array", items: [...] }, data = [5, "nine"], pointer = #
// 2. schema = { type: "number" }, data = 5, pointer = #/0
// 3. schema = { type: "string" }, data = "nine", pointer = #/1
});

Add custom validators

import { addValidator } from "json-schema-library";

// add a custom format 'id'
addValidator.format(core, "id", (core, schema, value, pointer) => {});

// add custom keyword 'capitalized' for type 'string'
addValidator.keyword(core, "string", "capitalized", (core, schema, value, pointer) => {});

// add a custom error (may overwrite existing errors)
addValidator.error(core, "minLengthError", (data) => ({
    type: "error",
    code: "custom-min-length-error",
    message: "my custom error message",
    data
}));

Additional helpers

getChildSchemaSelection(core, key, schema)

Returns a list of possible schemas for the given child-property or index

import { getChildSchemaSelection } from "json-schema-library";
const listOfAvailableOptions = getChildSchemaSelection(core, "childKey", schema);

createSchemaOf(data)

Creates a json-schema for the given input-data.

import { createSchemaOf } from "json-schema-library";
const baseSchema = createSchemaOf({ target: "" });
// returns {type: "object", properties: { target: "string"}},

eachSchema(schema, callback)

Iterate the schema, invoking the callback function for each type (schema) definition

import { eachSchema } from "json-schema-library";
const baseSchema = eachSchema(schema, (schema, pointer) => {});

Custom extensions

pattern

For error generation, an attribute patternExample may be set for a pattern validation. Instead of the regular expression, the example will be printed in the error message.

oneOf-flag

In resolveOneOf.fuzzy.js For an explicit oneOf resolution the schema may be extended by a oneOfProperty-property. This will always associate an entry with a matching value (instead of schema validation).

Example

const schema = {
    oneOfProperty: "id",
    oneOf: [
        { type: "object", properties: { id: { type: "string", pattern: "^1$" }, title: { type: "number" } } },
        { type: "object", properties: { id: { type: "string", pattern: "^2$" }, title: { type: "number" } } },
        { type: "object", properties: { id: { type: "string", pattern: "^3$" }, title: { type: "number" } } }
    ]
}

const result = resolveOneOf(core, { id: "2", title: "not a number" }, schema);
// will always return (even if invalid)
// { type: "object", properties: { id: { type: "string", pattern: "^2$" }, title: { type: "number" } } }

benurb/json-schema-library