sniptt/guards, a comprehensive collection of type guards for TypeScript.

In this article, we review snippt/guards. You will learn the following:

1. What is sniptt/guards?

2. Guards usage in Twenty codebase.

What is sniptt/guards?

Sniptt/guards is a comprehensive collection of type guards for JavaScript and TypeScript; Inspired by Elixir. Has zero dependencies. 

Foreword on JavaScript data types and data structures

The latest ECMAScript standard defines nine types:

• Six Data Types that are primitives, checked by typeof operator:

undefined: typeof instance === "undefined"
Boolean: typeof instance === "boolean"
Number: typeof instance === "number"
String: typeof instance === "string"
BigInt: typeof instance === "bigint"
Symbol: typeof instance === "symbol"

• Structural Types:

• Object: typeof instance === "object". Special non-data but structural type for any constructed object instance also used as data structures: new Object, new Array, new Map, new Set, new WeakMap, new WeakSet, new Date and almost everything made with new keyword;

• Function non data structure, though it also answers for typeof operator: typeof instance === "function". This answer is done as a special shorthand for Functions, though every Function constructor is derived from Object constructor.

• Structural Root Primitive

• null: typeof instance === "object". Special primitive type having additional usage for it's value: if object is not inherited, then null is shown;

Source: Guards Readme

Below is a simple example usage from the docs:

import { primitives } from '@sniptt/guards';
 
primitives.isNumber(val);

Guards usage in Twenty codebase.

I found the below code in Twenty codebase.

import { isNull, isUndefined } from '@sniptt/guards';
 
export const isDefined = <T>(
  value: T | null | undefined,
): value is NonNullable<T> => !isUndefined(value) && !isNull(value);

isUndefined is defined as shown below in the Guards docs.

import { isUndefined } from '@sniptt/guards';
 
let val: undefined | null;
 
if (isUndefined(val)) {
  // TypeScript will infer val: undefined
} else {
  // TypeScript will infer val: null
}

and this isDefined is used in usePlan hook as shown below:

import { isDefined } from 'twenty-shared/utils';
 
export const usePlans = () => {
  const { data, loading, error } = useListPlansQuery();
 
  const isPlansLoaded = isDefined(data?.listPlans);

About me:

Hey, my name is Ramu Narasinga. Email: ramu.narasinga@gmail.com

Tired of AI-generated code that works but nobody understands?

I spent 3+ years studying OSS codebases and wrote 350+ articles on what makes them production-grade. I built an open source tool that reviews your PR against your existing codebase patterns.

Your codebase. Your patterns. Enforced.

Get started for free — thinkthroo.com

References:

1. twenty/packages/twenty-shared/…/isDefined.ts#L1C1-L5C69

2. https://github.com/sniptt-official/guards

3. sniptt-official/guards?tab=…-data-structures

4. sniptt-official/guards?tab=readme-ov-file#isundefined