sindresorhus/is
Type check values · TypeScript · ★ 1,790
Analyzed at 7821031c66 on 2026-07-31. 100 documented errors.
| Code / Message | Type | Severity | Tags |
|---|---|---|---|
| Please don't use object wrappers for primitive types | exception | error | typescript, type-detection, boxed-primitive, anti-pattern |
| Invalid predicate array | validation | error | validation, predicate, empty-array |
| Invalid predicate: ${JSON.stringify(predicate)} | validation | error | validation, predicate, api-misuse |
| Invalid range: ${JSON.stringify(range)} | validation | error | validation, range, nan, numbers |
| Invalid number of values | validation | error | validation, empty-array, predicate |
| Expected value which is not `${description}`, received value | validation | error | assertion, runtime-check, null-safety |
| Expected values which are ${orFormatter.format(uniqueExpecte | validation | error | assertion, type-mismatch, validation |
| Expected value which is `Array`, received value of type `${i | validation | error | type-assertion, array, runtime-validation |
| Expected value which is `ArrayBuffer`, received value of typ | validation | error | type-assertion, binary-data, arraybuffer |
| Expected value which is `array-like`, received value of type | validation | error | type-assertion, array-like, runtime-validation |
| Expected value which is `AsyncFunction`, received value of t | validation | error | type-assertion, async, transpilation |
| Expected value which is `AsyncGenerator`, received value of | validation | error | type-assertion, async-generator, iteration |
| Expected value which is `AsyncGeneratorFunction`, received v | validation | error | type-assertion, async-generator, function-signature |
| Expected value which is `AsyncIterable`, received value of t | validation | error | type-assertion, async-iterable, iteration |
| Expected value which is `bigint`, received value of type `${ | validation | error | type-assertion, bigint, serialization |
| Expected value which is `BigInt64Array`, received value of t | validation | error | type-assertion, typed-array, bigint, binary-data |
| Expected value which is `BigUint64Array`, received value of | validation | error | type-assertion, typed-array, bigint, runtime-validation |
| Expected value which is `Blob`, received value of type `${is | validation | error | type-assertion, blob, binary-data, node |
| Expected value which is `boolean`, received value of type `$ | validation | error | type-assertion, boolean, config, coercion |
| Expected value which is `bound Function`, received value of | validation | error | type-assertion, function-binding, this-context |
| Expected value which is `Buffer`, received value of type `${ | validation | error | type-assertion, node, buffer, uint8array, cross-platform |
| Expected value which is `Class`, received value of type `${i | validation | error | type-assertion, class, transpilation, typescript |
| Expected value which is `DataView`, received value of type ` | validation | error | type-assertion, dataview, binary-data, typed-array |
| Expected value which is `Date`, received value of type `${is | validation | error | type-assertion, date, serialization, json |
| Expected value which is `T`, received value of type `${is(in | validation | error | type-assertion, instanceof, prototype, realm, dependency-duplication |
| Expected value which is `empty array`, received value of typ | validation | error | type-assertion, array, empty-check, invariant |
| Expected value which is `empty map`, received value of type | validation | error | type-assertion, runtime-validation, map, typescript |
| Expected value which is `empty object`, received value of ty | validation | error | type-assertion, runtime-validation, object, typescript |
| Expected value which is `empty set`, received value of type | validation | error | type-assertion, runtime-validation, set, typescript |
| Expected value which is `empty string`, received value of ty | validation | error | type-assertion, runtime-validation, string, typescript |
| Expected value which is `empty string or whitespace`, receiv | validation | error | type-assertion, runtime-validation, string, whitespace, typescript |
| Expected value which is `EnumCase`, received value of type ` | validation | error | type-assertion, runtime-validation, enum, typescript |
| Expected value which is `Error`, received value of type `${i | validation | error | type-assertion, runtime-validation, error-handling, typescript |
| Expected value which is `even integer`, received value of ty | validation | error | type-assertion, runtime-validation, number, integer |
| Expected value which is `falsy`, received value of type `${i | validation | warning | type-assertion, runtime-validation, truthiness, javascript |
| Expected value which is `finite number`, received value of t | validation | error | type-assertion, runtime-validation, number, nan, typescript |
| Expected value which is `Float32Array`, received value of ty | validation | error | typescript, type-assertion, typed-array, runtime-validation |
| Expected value which is `Float64Array`, received value of ty | validation | error | typescript, type-assertion, typed-array, runtime-validation |
| Expected value which is `FormData`, received value of type ` | validation | error | form-data, type-assertion, runtime-validation, node |
| Expected value which is `Function`, received value of type ` | validation | error | callback, type-assertion, runtime-validation, javascript |
| Expected value which is `Generator`, received value of type | validation | error | generator, iterator, type-assertion, runtime-validation |
| Expected value which is `GeneratorFunction`, received value | validation | error | generator, transpilation, type-assertion, runtime-validation |
| Expected value which is `HTMLElement`, received value of typ | validation | error | dom, browser, ssr, type-assertion |
| Expected value which is `infinite number`, received value of | validation | error | number, infinity, json, type-assertion |
| Expected value which is `in range`, received value of type ` | validation | error | number, range, input-validation, type-assertion |
| Expected value which is `Int16Array`, received value of type | validation | error | typed-array, binary-data, type-assertion, runtime-validation |
| Expected value which is `Int32Array`, received value of type | validation | error | typed-array, type-assertion, typescript |
| Expected value which is `Int8Array`, received value of type | validation | error | typed-array, buffer, node, type-assertion |
| Expected value which is `integer`, received value of type `$ | validation | error | number, validation, type-assertion |
| Expected value which is `Iterable`, received value of type ` | validation | error | iterable, iteration, type-assertion |
| Expected value which is `Map`, received value of type `${is( | validation | error | map, serialization, type-assertion |
| Expected value which is `NaN`, received value of type `${is( | validation | warning | number, nan, type-assertion |
| Expected value which is `native Promise`, received value of | validation | error | promise, async, type-assertion |
| Expected value which is `negative integer`, received value o | validation | error | number, validation, type-assertion |
| Expected value which is `negative number`, received value of | validation | error | number, validation, type-assertion |
| Expected value which is `Node.js Stream`, received value of | validation | error | stream, node, type-assertion |
| Expected value which is `non-empty array`, received value of | validation | error | assertion, type-check, array, typescript |
| Expected value which is `non-empty map`, received value of t | validation | error | assertion, type-check, map, typescript |
| Expected value which is `non-empty object`, received value o | validation | error | assertion, type-check, object, typescript |
| Expected value which is `non-empty set`, received value of t | validation | error | assertion, type-check, set, typescript |
| Expected value which is `non-empty string`, received value o | validation | error | assertion, type-check, string, environment, typescript |
| Expected value which is `non-empty string and not whitespace | validation | error | assertion, type-check, string, validation, input-sanitization |
| Expected value which is `non-negative integer`, received val | validation | error | assertion, type-check, number, integer, validation |
| Expected value which is `non-negative number`, received valu | validation | error | assertion, type-check, number, validation |
| Expected value which is `null`, received value of type `${is | validation | error | assertion, type-check, null, typescript |
| Expected value which is `null or undefined`, received value | validation | error | assertion, type-check, null, undefined, state-management |
| Expected value which is `number`, received value of type `${ | validation | error | type-check, assertion, runtime-validation, typescript |
| Expected value which is `string with a number`, received val | validation | error | type-check, assertion, string-validation, runtime-validation |
| Expected value which is `Object`, received value of type `${ | validation | error | type-check, assertion, null-check, runtime-validation |
| Expected value which is `Observable`, received value of type | validation | error | type-check, assertion, observable, rxjs, interop |
| Expected value which is `odd integer`, received value of typ | validation | error | type-check, assertion, number-validation, integer |
| Expected value which is `plain object`, received value of ty | validation | error | type-check, assertion, plain-object, runtime-validation |
| Expected value which is `positive integer`, received value o | validation | error | type-check, assertion, number-validation, integer, input-validation |
| Expected value which is `positive number`, received value of | validation | error | type-check, assertion, number-validation, input-validation |
| Expected value which is `primitive`, received value of type | validation | error | type-check, assertion, primitive, runtime-validation |
| Expected value which is `Promise`, received value of type `$ | validation | error | type-check, assertion, promise, async |
| Expected value which is `PropertyKey`, received value of typ | validation | error | typescript, type-assertion, validation, property-key |
| Expected value which is `RegExp`, received value of type `${ | validation | error | typescript, type-assertion, regexp, validation |
| Expected value which is `safe integer`, received value of ty | validation | error | typescript, type-assertion, number, integer-overflow, validation |
| Expected value which is `Set`, received value of type `${is( | validation | error | typescript, type-assertion, collections, serialization |
| Expected value which is `SharedArrayBuffer`, received value | validation | error | typescript, type-assertion, shared-array-buffer, web-workers, cross-origin-isolation |
| Expected value which is `string`, received value of type `${ | validation | error | typescript, type-assertion, string, validation, environment-variables |
| Expected value which is `symbol`, received value of type `${ | validation | error | typescript, type-assertion, symbol, validation |
| Expected value which is `truthy`, received value of type `${ | validation | warning | typescript, type-assertion, truthy, falsy, validation |
| Expected value which is `tuple-like`, received value of type | validation | error | typescript, type-assertion, tuple, array, validation |
| Expected value which is `TypedArray`, received value of type | validation | error | typescript, type-assertion, typed-array, binary-data, validation |
| Expected value which is `Uint16Array`, received value of typ | validation | error | typescript, type-assertion, typed-array, runtime-validation |
| Expected value which is `Uint32Array`, received value of typ | validation | error | typescript, type-assertion, typed-array, runtime-validation |
| Expected value which is `Uint8Array`, received value of type | validation | error | typescript, type-assertion, typed-array, binary-data |
| Expected value which is `Uint8ClampedArray`, received value | validation | error | typescript, type-assertion, typed-array, canvas |
| Expected value which is `undefined`, received value of type | validation | error | typescript, type-assertion, null-vs-undefined |
| Expected value which is `URL`, received value of type `${is( | validation | error | typescript, type-assertion, url |
| Expected value which is `URLSearchParams`, received value of | validation | error | typescript, type-assertion, url, query-string |
| Expected value which is `string with a URL`, received value | validation | error | typescript, type-assertion, url, validation |
| Expected value which is `valid Date`, received value of type | validation | error | typescript, type-assertion, date, validation |
| Expected value which is `valid length`, received value of ty | validation | error | typescript, type-assertion, number, validation |
| Expected value which is `WeakMap`, received value of type `$ | validation | error | typescript, type-assertion, weakmap, runtime-validation, sindresorhus-is |
| Expected value which is `WeakRef`, received value of type `$ | validation | error | typescript, type-assertion, weakref, garbage-collection, runtime-validation, sindresorhus-is |
| Expected value which is `WeakSet`, received value of type `$ | validation | error | typescript, type-assertion, weakset, runtime-validation, sindresorhus-is |
| Expected value which is `whitespace string`, received value | validation | error | typescript, type-assertion, string-validation, whitespace, runtime-validation, sindresorhus-is |