@philiprehberger/ts-guard

Runtime type guard utilities with TypeScript narrowing.

Installation

npm install @philiprehberger/ts-guard

Usage

import { isString, isNumber, isArrayOf, isObjectWith, assert } from '@philiprehberger/ts-guard';

if (isString(val)) {
  val.toUpperCase(); // narrowed to string
}

const isUser = isObjectWith({
  name: isString,
  age: isNumber,
});

if (isUser(data)) {
  data.name; // typed as string
  data.age;  // typed as number
}

assert(input, isArrayOf(isString)); // throws or narrows to string[]

Composing Guards

import { isOneOf, isString, isNumber, isTupleOf } from '@philiprehberger/ts-guard';

const isStringOrNumber = isOneOf(isString, isNumber);
const isPair = isTupleOf(isString, isNumber);

isStringOrNumber('hello'); // true
isPair(['hello', 42]);     // true

API

| Function | Description | |----------|-------------| | isString, isNumber, isBoolean, isNull, isUndefined, isNil, isBigInt, isSymbol | Primitive guards | | isArray, isObject, isPlainObject, isMap, isSet, isDate, isRegExp, isError, isPromise, isFunction | Structural guards | | isNonEmpty, isPositive, isNegative, isInteger, isFiniteNumber, isNonNullish | Value guards | | isOneOf(...guards) | Union of guards | | isArrayOf(guard) | Array where all items match guard | | isObjectWith(shape) | Object matching shape of guards | | isTupleOf(...guards) | Tuple matching guards positionally | | assert(value, guard, message?) | Throw if guard fails, narrow otherwise |

Development

npm install
npm run build
npm test

License

MIT