npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

required-properties

v1.1.3

Published

Assert required properties of object with full typescript support

Downloads

12

Readme

required-properties

Validates required properties in a given object with full TypeScript support 🚀

Installation

npm i required-properties

Motivation

When we know that some property in object is not null or undefined, we can check for it. But TypeScript is not able to infer the type of original object. 😱

Usecase #1

interface Data {
    value: string | null;
}

declare function mockDbQuery(): Data

const getNonNullableData = () => {
    const dbResult = mockDbQuery()

    // by some business logic, we know that value is not null
    if (dbResult.value === null) {
        throw new Error("value is null!")
    }

    return dbResult
}

const data = getNonNullableData()
data.value // -> string | null ❌ (expected only string)

TS playground: link

Usecase #2

interface Person {
    firstName: string | null;
    lastName: string;
}

const person: Person = {
    firstName: "John",
    lastName: "Doe",
};

function printFullName(names: { firstName: string; lastName: string }) {
    console.log(`${names.firstName} ${names.lastName}`);
}

// original approach
if (person.firstName === null) {
    throw new Error("firstName is required");
}

printFullName(person); // ❌ this results in TS error, because person is still of type Person which has nullable property firstName

TS playground: link

Usage

assertRequiredProperties

  • first parameter is object you want to validate
  • second argument is an array of properties which can be null or undefined. You can access nested properties using dot separator

Solution for Usecase #1

import {assertRequiredProperties} from "required-properties";

interface Data {
    value: string | null;
}

declare function mockDbQuery(): Data

const getNonNullableData = () => {
    const dbResult = mockDbQuery()

    assertRequiredProperties(dbResult, ["value"]) // 👈 this changes type of dbResult

    return dbResult
}

const data = getNonNullableData()
data.value // -> string ✅

Solution for Usecase #2

import {assertRequiredProperties} from "required-properties";

interface Person {
    firstName: string | null;
    lastName: string;
}

const person: Person = {
    firstName: "John",
    lastName: "Doe",
};

function printFullName(names: { firstName: string; lastName: string }) {
    console.log(`${names.firstName} ${names.lastName}`);
}

// assertRequiredProperties approach
assertRequiredProperties(person, ["firstName"]); // 👈 this changes type of person
printFullName(person); // ✅ this is now valid TS code

It comes with full TypeScript support (also for nested nullable properties): typescript intellisense required properties