Category: validation Since: 1.0.0 Tags: validation, type-guard, string, literal

isEmptyString

Checks whether the provided value is the empty string literal.

Usage

import { isEmptyString } from "@petr-ptacek/js-core";

const values = ["", "text", null, undefined];

values.forEach((value) => {
  console.log(`${JSON.stringify(value)} is empty string:`, isEmptyString(value));
});

Why This Utility Exists

Native runtime checks (value === "") are trivial, but without a helper you lose TypeScript type narrowing. isEmptyString provides a dedicated type guard that keeps type information straight in generic code, validation flows, and unknown inputs.

Signature

function isEmptyString(value: unknown): value is "";

Parameters

• value (unknown): The value to test.

Return Type

Returns true when the input is exactly "", false otherwise. When the function returns true, TypeScript infers the literal type "".

Design Notes

1. Based on the strict equality check (value === ""), so it keeps zero runtime overhead and behaves identically to vanilla JS.
2. Acts as a TypeScript type guard allowing downstream code to work with the empty string literal without additional assertions.

When To Use

• When you need to ensure a value is literally the empty string before calling string-specific APIs.
• In form validation or normalization helpers where empty strings must be treated differently from null/undefined.
• When typing branches that depend on empty-string-specific logic for TypeScript.

When Not To Use

• When you already statically know the value is a string.
• When you only care about truthiness/falsiness rather than the literal "".

Summary

isEmptyString keeps validation readable while giving TypeScript the literal type information it needs for empty-string-specific paths.

Snippets

basic.ts

import { isEmptyString } from "@petr-ptacek/js-core";

const values = ["", "  ", null, undefined, 0, "text"];

values.forEach((value) => {
  console.log(`${JSON.stringify(value)} is empty string:`, isEmptyString(value));
});