typescript-field-validation

Basic tools for NonNullable type manipulation and validation.

There are two tools exposed in this library which are designed to work together:

• SetRequired (conditional type)
• validate (function)

SetRequired allows you to take a type and declare fields to be Required and NonNullable.

validate checks if the required fields are present and not null or undefined.

Both SetRequired and validate use the same syntax for requiring fields. This means you can perform type manipulations and data validation by decalring the required fields once.

Syntax

To specify a field as being required simply use that fields name. To specify a sub field on a field use dot notation field.subField. To specify a required field for every object in a field that is an array use []. For example fieldOne[].subField would mean that fieldOne is an array and every member of that array needs to have a subField.

Example usage

import { validate, SetRequired } from 'typescript-field-validation';

type TypeWithOptionalFields = {
  id?: string;
  item?: {
    items?: { id?: string; value: any | null }[];
  };
  link?: string;
  date?: number;
};

const requiredFields = ['id', 'item.items[].id', 'item.items[].value', 'date'] as const;

type TypeWithNonOptionFields = SetRequired<TypeWithOptionalFields, typeof requiredFields[number]>;

const invalidData = {
  id: '12345',
  item: {
    items: [{ value: 'hello world' }],
  },
};

// Default: Provides maximum information regarding what fields were missing
const result1 = validate(invalidData, requiredFields);
console.log('Default', result1);
/**
{
  invalidFields: { date: 'is missing', 'item.items[0].id': 'is missing' },
  validType: null
}
 */

// No index: Removes the array index for missing fields.
const result2 = validate(invalidData, requiredFields, {
  includeIndex: false,
});
console.log('No array index', result2);
/**
{
  invalidFields: { date: 'is missing', 'item.items[].id': 'is missing' },
  validType: null
}
*/

// Fail fast: Returns the first failure at the lowest depth
const result3 = validate(invalidData, requiredFields, {
  failFast: true,
});
console.log('Fail fast', result3);
/**
 { invalidFields: { date: 'is missing' }, validType: null }
 */

// Raw fields: Returns an error object whose shape mimicks the data
const result4 = validate(invalidData, requiredFields, {
  rawFields: true,
});
console.log('Raw fields', JSON.stringify(result4, null, 2));
/**
 {
  "invalidFields": {
    "date": "is missing",
    "item": {
      "items": [
        {
          "id": "is missing"
        }
      ]
    }
  },
  "validType": null
}
 */

const validData = {
  id: '12345',
  item: {
    items: [{ id: 'myId', value: 'hello world' }],
  },
  date: 1627787814504,
};

const result5: TypeWithNonOptionFields | null = validate(validData, requiredFields).validType;

if (result5) {
  console.log('Result is valid type: 'true);
  // true
}

---

A note of warning: This tool does not check that the values of the required fields are of the type defined by the base type, this is assumed to be correct. Rather, it simply makes a field required and removes undefined | null from the fields union type.

---

CHANGELOG

• 2.0.3: Fix: Missing array items keep their index when previous elements passed

• 2.0.2: Inlining of small helper functions to minimize code

• 2.0.1: Fix: failFast option returns single result for array fields

• 2.0.0:

  • validate function uses a breadth first search over a generated search graph
  • validate function takes additional parameters to failFast and other formatting options of error messages

  Breaking changes:

  • Package now targets es2019
  • validate now returns missing fields as a Record<field, error message>
  • validate now optionally returns missing fields in the same shape as the provided data when the rawFields option is set to true.

• 1.1.2: Add MIT license

• 1.1.1: Update Result type to be a exclusive or union of pass or fail types

• 1.1.0: Improve error messages and add additional checks for object vs array fields

• 1.0.1: Update readme