Utility to valide objects in TypeScript

interface User {
  name: string;
  age?: number;
  isAdmin?: boolean;
  capabilities?: string[];
  attributes?: { [key: string]: string };
}

const user = {name: 'Maximus', capabilities: [], attributes: {handsome: 'very'}};

const validationRules = {
  name: [isNotEmpty, name => minLength(name, 3)],
  capabilities: [isNotEmpty],
  attributes: [isNotEmpty],
};

const results = validate<User>(user, validationRules); // {name: true, capabilities: false, attributes: true}
const isValid = isValid<User>(user, validationRules); // false

const user = {name: 'Maximus'};
const validationRules = {fullName: [isNotUndefined]}

validate<User>(user, validationRules);
                     ^^^^^^^^^^^^^^^
                     'fullName' doesn't exist on type User

• isNotNull
  • Checks if the value is null
• isNotUndefined
  • Checks if the value is undefined
• isRequired
  • Checks if the value is truthy
• minLength
  • Checks if the value's length is above (or equal) the specified minimum treshold.
  • Usage: {propertyName: [value => minLength(value, 5)]}
• maxLength
  • Checks if the value's length is below (or equal) the specified maximum treshold.
  • Usage: {propertyName: [value => maxLength(value, 5)]}
• isNotEmpty
  • Checks if the string, array, or Object.keys()'s length is truthy
• isEnumSubset
  • Checks if the values inside an array are (or a single value is) valid values for a given Enum
  • Usage: {propertyName: [value => isValidForEnum(value, EnumType)]

• validate<T>(unitUnderTest: T, validators: {[K in keyof Partial<T>]: Function[]}): {[K in keyof Partial<T>]: boolean}
  • Will return the same structure as Partial<T> (that are the fields to be validated), with a single boolean for each test to indicate if it is passing
• isValid<T>(unitUnderTest: T, validators: {[K in keyof Partial<T>]: Function[]}): boolean
  • Will return a single boolean (using validate() under the hood) signaling the combined status of all tests

Providing custom validator functions are as easy as 🔢

const user = {name: 'Maximus'};
const validationRules = {name: [name => name === 'Maximus', name => console.log(name)]};

const isValid = isValid<User>(user, validationRules); // true

The custom validator functions should return a boolean, to be usable for validation. If the function is void, it'll return true as in "I found this test to be passing 🤔".

Feel free to open a PR with a brief description about the changes.
Don't forget to cover your changes with (passing) tests!

To install, clone the repo & yarn install.
To run tests, you can just simply type yarn jest in your terminal.