default-value-to

A tiny TypeScript utility to safely transform undefined or null values into predictable defaults — designed to simplify unit testing and improve branch coverage.

Why This Package?

When mapping API data into strongly typed objects, source data often returns:

• string | undefined
• number | undefined

To make values safe, we usually write:

obj?.prop ?? ""

or

obj?.count ?? 0

However, in unit tests, using optional chaining (?.) creates additional branches that must be covered.

For example:

obj?.prop ?? ""

To achieve full coverage, you must mock:

• obj undefined
• obj defined but prop undefined
• obj.prop defined

That increases unnecessary test complexity.

The Solution

default-value-to centralizes that nullish handling into a single utility:

defaultTo(obj?.prop, "")

Now your unit tests only need to test:

• value defined
• value undefined

No deep object mocking required.

Installation

npm install default-value-to

Usage

import { defaultTo } from "default-value-to";

type User = {
  name?: string;
  age?: number;
};

const user = undefined;

const name = defaultTo(user?.name, "");
const age = defaultTo(user?.age, 0);

Resulting Types

name: string
age: number

Never undefined.

API

defaultTo<T>(value: T, defaultValue: NonNullable<T>): NonNullable<T>

Returns:

• value if not null or undefined
• defaultValue otherwise

Example: Mapping API Data

Before:

const mapped = {
  name: apiUser?.name ?? "",
  age: apiUser?.age ?? 0
};

After:

const mapped = {
  name: defaultTo(apiUser?.name, ""),
  age: defaultTo(apiUser?.age, 0)
};

Cleaner.
More readable.
Less test boilerplate.

Designed For

• React projects
• TypeScript projects
• Clean unit test coverage
• API data transformation layers

License

MIT