Neurosis Prevention Mechanism
    Wondering what’s next for npm?Check out our public roadmap! »

    @lucaspaganini/playground
    TypeScript icon, indicating that this package has built-in type declarations

    0.0.0 • Public • Published

    Value Objects

    A TypeScript first validation and class creation library. Learn in 10 minutes with the quickstart.

    • 100% typed
    • 100% tested
    • Simple syntax
    • Zero dependencies
    • Exported in ES5

    IMPORTANT: About the package size

    NPM's "Unpacked Size" is innacurate because the package includes source maps and source files for easier debugging. So, the accurate size of this library for most users is this:

    Version 1.3.0 Size
    Unpacked 46.27 KB
    Minified bundle 19.68 KB
    Gzipped minified bundle 4.58 KB

    Motivation

    If you have to represent the user age in years, would you use a string or a number? Doesn't matter, they're both not ideal. Every age in years could be represented as a string or as a number, but not every string or number could represent a valid age.

    Value objects to the rescue: If you want an age, create an Age object.

    class Age {
      private _value: number;
     
      constructor(raw: number) {
        if (raw < 0) throw Error('Too small');
        if (raw > 150) throw Error('Too big');
        if (!Number.isInteger(raw)) throw Error('Not an integer');
        this._value = raw;
      }
     
      valueOf(): number {
        return this._value;
      }
     
      toMonths(): number {
        return this.valueOf() * 12;
      }
    }

    But that's ugly, so I made this library to ease your pain.

    import { VOInteger } from '@lucaspaganini/value-objects';
     
    class Age extends VOInteger({ min: 0, max: 150 }) {
      toMonths(): number {
        return this.valueOf() * 12;
      }
    }

    Compatibility

    Package version TypeScript version
    1.x.x >= 2.8.1

    Usage

    Creating value objects

    import {
      VOString,
      VOInteger,
      VOSet,
      VOArray,
      VOObject
    } from '@lucaspaganini/value-objects';
     
    const EMAIL_PATTERN = /^(?=.{1,254}$)(?=.{1,64}@)[-!#$%&'*+/0-9=?A-Z^_`a-z{|}~]+(\.[-!#$%&'*+/0-9=?A-Z^_`a-z{|}~]+)*@[A-Za-z0-9]([A-Za-z0-9-]{0,61}[A-Za-z0-9])?(\.[A-Za-z0-9]([A-Za-z0-9-]{0,61}[A-Za-z0-9])?)*$/;
    export class Email extends VOString({
      trim: true,
      maxLength: 256,
      pattern: EMAIL_PATTERN
    }) {
      getHost(): string {
        const arr = this.valueOf().split('@');
        return arr[arr.length - 1];
      }
    }
     
    const PASSWORD_PATTERN = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)[a-zA-Z\d]*$/; // One lowercase, one uppercase, one number
    class Password extends VOString({
      trim: false,
      minLength: 8,
      maxLength: 256,
      pattern: PASSWORD_PATTERN
    }) {}
     
    class Age extends VOInteger({ min: 0, max: 150 }) {
      toMonths(): number {
        return this.valueOf() * 12;
      }
    }
     
    class NetflixShow extends VOSet([
      'You',
      'House of Cards',
      'Sense8',
      'The Witcher'
    ]) {}
     
    class NetflixShows extends VOArray(NetflixShow, { minLength: 1 }) {}
     
    class User extends VOObject({
      email: Email,
      password: Password,
      age: Age,
      favoriteShows: NetflixShows
    }) {}

    Type safety

    const userError = new User({
      email: '', // RUNTIME ERROR: Will throw when trying to instantiate an Email with an empty string, but it's still a `string` so it's type is correct
      password: 123, // COMPILATION ERROR: TypeScript expects a `string` because that's what the Password constructor expects
      age: 21.5, // RUNTIME ERROR: Will throw when trying to instantiate an Age with a non integer number. If you want a float, you can extend `VOFloat()`
      favoriteShows: ['Lost'] // RUNTIME ERROR: "Lost" is not in the set. You might think it shouldn't accept any string, but it's a design decision (see VOSet in the docs)
    });
     
    const userSuccess = new User({
      email: 'test@example.com',
      password: '123abcABC',
      age: 150,
      favoriteShows: ['You', 'House of Cards']
    });

    Validating / instantiating objects

    import { makeFromRawInit } from '@lucaspaganini/value-objects';
     
    const userFromRaw = makeFromRawInit(User);
    userFromRaw({}); // COMPILATION ERROR: It expects a correct raw user structure
     
    app.post('/api/create-user', (req, res) => {
      const userEither = userFromRaw(req.body as any);
      if (userEither._tag === 'Left')
        return res.status(400).json({ errors: userEither.left });
      const user = userEither.right;
     
      const createdUser = createUser(user);
      res.status(200).json({ user: createdUser });
    });

    Resources

    Install

    npm i @lucaspaganini/playground

    DownloadsWeekly Downloads

    0

    Version

    0.0.0

    License

    MIT

    Unpacked Size

    192 kB

    Total Files

    82

    Last publish

    Collaborators

    • avatar