get-or-throw

A convenience function for adhering to Typescript's noUncheckedIndexedAccess setting.

Get a value from an object or array at the specified key or index. Throw an error if the key or index does not exist, or if the resulting value is undefined or null.

Features

• Uses Typescript assertions for type narrowing.
• Works with both objects and arrays.
• Supports negative indexing for arrays.
• Allows for custom error messages.
• Zero dependencies.

Installation

pnpm add get-or-throw

...or use the equivalent for your package manager.

Usage

const arr = [1, 2, 3];
console.log(getOrThrow(arr, 1)); // Output: 2

/** Support for negative indexing */
const arr = [1, 2, 3];
console.log(getOrThrow(arr, -1)); // Output: 3

/** This will throw an error: "Index 3 is out of bounds." */
console.log(getOrThrow(arr, 3));

const obj = { a: 1, b: 2, c: 3 };
console.log(getOrThrow(obj, "b")); // Output: 2

/** This will throw an error: "Key "d" does not exist in the object." */
console.log(getOrThrow(obj, "d"));

/** This will throw an error: "Failed to find d" */
const key = "d";
console.log(getOrThrow(obj, key, `Failed to find ${key}`));

/** This will throw an error: "Value at index 1 is undefined or null." */
const arr = [1, null, 3];
console.log(getOrThrow(arr, 1));

/** This will throw an error: "Value at index 1 is undefined or null." */
const arr = [1, undefined, 3];
console.log(getOrThrow(arr, 1));

/** This will throw an error: "Value at key 'b' is undefined or null." */
const obj = { a: 1, b: undefined, c: 3 };
console.log(getOrThrow(obj, "b"));