policeman

Lightweight yet powerful schema validator

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API Docs | Examples

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• Validate objects based on provided schema
• Inspired by mappet

Installation (npm)

npm i -S policeman

Examples

import policeman, { isRequired, isEmail, isMatching, combineValidators } from "policeman";

// setup entry validators
const requiredValidator = isRequired(() => "is required");
const emailValidator = isEmail(() => "is invalid email");
const phoneNumberValidator = isMatching(/\d{3}-?\d{3}-?\d{3}/, () => "is invalid phone");

// setup entry filter predicates
const isGift = (value, source) => source.gift === true;

// define schema
const schema = [
  // 1. array of validators - multiple errors
  // 2. combine validators - first of many errors
  // 3. single validator - single error
  // 4. skip validation based on filter predicate

  ["email", "email", [requiredValidator, emailValidator]], // #1
  ["phone", "phone", combineValidators(requiredValidator, phoneNumberValidator)], // #2
  ["name", "name", requiredValidator], // #3
  ["giftCode", "giftCode", requiredValidator, isGift], // #4
  // [dest, source, Validator, Filter]
];

// create validator
const validator = policeman(schema);

// validate
validator({ gift: false, email: "invalid@example", phone: "777-666-55" });

// {
//   valid: false,
//   errors: {
//     email: ["is invalid email"],
//     phone: "is invalid phone",
//     name: "is required"
//   }
// }

See tests for more examples.

Built-in validators

All built-in validators are curried.

isRequired(() => message, value)

Validates presence. Fails on null, empty string or undefined.

isMinLength(min, () => message, value)

Passed value must be a string longer or with length equal to min.

isMaxLength(max, () => message, value)

Passed value must be a string shorther or with length equal to max.

isEqualLength(equal, () => message, value)

Passed value must be a string shorther or with length equal to max.

isEmail(() => message, value)

Passed value must be a valid email. It's a simple check, if you need more complex solution use isMatching or isPassing.

isMatching(regexp, () => message, value)

Passed value must pass regexp.

isPassing(predicate, () => message, value)

Passed predicate answers on "Is value valid?". When predicate returns true validator passes, when predicate returns false error message is returned.

It makes policeman compatible with all available validators i.e. validator.

import validator from "validator";
import { isPassing } from "policeman";

const creditCardValidator = isPassing(validator.isCreditCard, () => "is invalid credit card");
const uuid4Validator = isPassing(value => validator.isUUID(value, 4), () => "is invalid UUID v4");
const ftpValidator = isPassing(value => validator.isURL(value, { protocols: ["ftp"] }, () => "is invalid FTP address");

See tests for more examples.