to-safe-integer

Converts any JavaScript value into an integer, safely — never returns NaN, always falls back to a sensible default.

Installation

npm install to-safe-integer

Usage

const toSafeInteger = require('to-safe-integer');

toSafeInteger(42);            // 42
toSafeInteger(42.9);          // 42 (truncated, not rounded)
toSafeInteger("42");          // 42
toSafeInteger("42px");        // 42 (PHP-style leading digit parsing)
toSafeInteger("px42");        // 0  (no leading digit, falls back)
toSafeInteger(null);          // 0
toSafeInteger(undefined);     // 0
toSafeInteger(true);          // 1
toSafeInteger(NaN);           // 0
toSafeInteger([42]);          // 42
toSafeInteger("abc", -1);     // -1 (custom fallback)

Why not just parseInt(value)?

• parseInt(null) returns NaN — this library returns a safe fallback instead.
• parseInt doesn't clamp Infinity or oversized BigInt values to a safe range.
• String parsing follows a PHP-style convention: a leading digit sequence is extracted ("42px" → 42), but a string that doesn't start with a digit falls back ("px42" → 0), unlike scanning for digits anywhere in the string.

API

toSafeInteger(value: any, fallback?: number = 0): number

Takes any value and always returns a safe integer — never throws, never returns NaN.

• fallback — value returned when value can't be meaningfully converted. Must itself be an integer; otherwise it's silently reset to 0.

License

MIT © Toby Maxham