Guesses the type of a value from its string form so you can stop writing repetitive parsing logic.

Install

npm install @fossiq/enval

Usage

import { enval } from "@fossiq/enval";

Booleans (case-insensitive)

enval("true"); // true
enval("YES"); // true
enval("off"); // false

Numbers (with safe integer protection for large numbers like Snowflake IDs)

enval("42"); // 42
enval("3.14"); // 3.14
enval("1234567890123456789"); // "1234567890123456789"

Nullish

enval("null"); // null
enval("undefined"); // undefined

JSON

enval("[1, 2, 3]"); // [1, 2, 3]
enval('{"enabled": true}'); // { enabled: true }

Strings (auto-unquoted and trimmed)

enval('"hello"'); // "hello"
enval("  text  "); // "text"

Constructor shorthand

enval('["a", "b", "a"]', Set); // Set(2) { "a", "b" }

Parsing Order

1. Nullish: null, undefined
2. Boolean: true, false, yes, no, on, off (case-insensitive)
3. Number: Numeric strings (with safe integer protection)
4. JSON: Objects {} and arrays []
5. String: Everything else

Nice to Know

TypeScript type hints

enval<string[]>('["a", "b"]'); // string[]
enval<{ host: string }>('{"host": "localhost"}'); // { host: string }

Optional values with defaults

const maxRetries = enval<number>(process.env.MAX_RETRIES) ?? 3;

Comma-separated values (when JSON arrays aren't an option)

const ports = enval("3000,3001,3002", (_, raw) =>
  (raw as string).split(",").map(Number),
); // [3000, 3001, 3002]

Validation at parse time

const port = enval(process.env.PORT, (inferred) => {
  const num = inferred as number;
  if (num < 1 || num > 65535) throw new Error(`Invalid port: ${num}`);
  return num;
});