json_schema

This is a dependency-free schema-based json validator designed to be used in browser

Supports the following data-types with their respective properties:

Type	Useful properties
number	minimum, maximum, enum
string	minLength, maxLength, pattern, enum
object	properties
array	minLength, maxLength, item_schema, enum

Every schema or subschema requires type.

Every schema has three common properties: name, description and required. It is a good practice to mention name and sufficient description for better feedback in case of errors.

Note:

1. required, minimum, maximum, minLength, maxLength and enum support callbacks but care should be taken while using them. If not provided default for required will be set to false.
2. item_schema is to be provided in case of array types, and the item_schema will be initialized for type mentioned in the item_schema.
3. object item_types are not checked for uniqueItems filter for array schemas.

Usage:

Step 1: Defining Schemas

Integer Schema

let product_id = {
  "required": true,
  "description":"This is the id for each product",
  "name": "Product ID",
  "type": "number",
  "minimum": 1
}

String Schema

let product_name = {
  "required": true,
  "description":"This is the name of each product",
  "name": "Product Name",
  "type": "string"
  "minLength": 3
}

Object Schema

let product = {
  "name": "Product",
  "description": "This is the object schema of each product - contains all the properties of a product",
  "type": "object",
  "required": true,
  "properties": {
    "product_name": product_name,
    "product_id": product_id
  }
}

Array Schema

let productSchema = {
  "name": "Products",
  "description": "Array of products",
  "required": true,
  "type": "array",
  "item_schema": product
}

Step 2: Initializing the schema

require('json_schema');

var mySchema = new Schema(productSchema)
    .then(res => res)
    .catch(err => {
        // some code to handle error
    })

Note:

new Schema(schema) returns a promise with all the values - default, defined. The promise resolves with the instance of the class and rejects with an error object that is structured with nested error bodies for nested schemas contains a message about the error in schema that was passed.

Step 3: Validating data objects

Call the myScema.validate(data) function which return a promise that can be handled appropriately

try {
    var json_to_validate = [
      {product_name: "Guitar"}, 
      {product_name: "Piano", product_id: 1} 
    ];

    var result = mySchema.validate(json_to_validate)
      .then(res => {
          return res; 
          // returns true if valid json is passed
      })
      .catch(err => {
          return err;
          // return detailed error
      });
}

This would result into an error because the product_id is not specified for product "Guitar".
obj.validate(data) returns the following error as a rejected promise

{ root: 'Products',
  description: 'Array of products',
  title: 'Products failed due to the following reason(s) at position 0.',
  body: 
   { root: 'Product ID',
     description: 'This is the id for each product',
     title: 'Product should have the property product_id',
     body: { message: 'Product should have the property product_id' 
    } 
  } 
}

Pretty simple and neat, right?

Advanced Usage:

Documentation for callback

Coming soon