@dndd/utils

Framework-agnostic helper functions with no runtime dependencies.

Install

npm install @dndd/utils

Type guards

import {
  isString,
  isNumber,
  isObject,
  isArray,
  isNullable,
  isBoolean,
  isFunction,
} from "@dndd/utils";

isString("hi"); // true
isNumber("42"); // true — numeric strings count
isObject([1, 2]); // false — arrays are excluded
isArray<number>(value); // value is number[]
isNullable(value); // value is null | undefined
isBoolean(true); // true
isFunction(() => {}); // true — also true for classes

Prefer these over raw typeof/instanceof checks — they narrow correctly and cover the edge cases (isNumber accepts finite numeric strings, isObject excludes arrays, isString covers boxed String instances).

invariant

import { invariant } from "@dndd/utils";

invariant(user, "user must be defined here");
user.name; // TypeScript now knows `user` is non-null

invariant(count > 0); // throws "Invariant failed" if the condition is falsy

Throws if the value is false, null, or undefined; narrows it afterward, so it also works as a type guard for assumptions the type system can't verify on its own.

ensureArray

import { ensureArray } from "@dndd/utils";

ensureArray("a"); // ["a"]
ensureArray(["a", "b"]); // ["a", "b"] — unchanged

Normalizes a value that may or may not already be an array — handy for props that accept T | T[].

Scope

Stays intentionally small — a place for the handful of type guards and primitives that get rebuilt in every project. For general-purpose data manipulation (grouping, sorting, deep operations, ...), reach for Remeda instead of expecting it here.