@haixing_hu/type-detect

type-detect

type-detect is a lightweight JavaScript library that provides utilities for detecting the type of JavaScript variables. It is designed to be compatible with the latest ECMAScript standards.

If you want to get more detailed type information of a variable, you can use the typeinfo library, which is built on top of type-detect.

Table of Contents

• Installation
• Usage
  • Type Detection Functions
  • Feature Detection Constants
  • Type Prototype Constants
• Why Proxy Type Cannot be Detected
• Contributing
• License

Installation

You can install type-detect via npm:

npm install @haixing_hu/type-detect

or via yarn:

yarn add @haixing_hu/type-detect

Usage

Type Detection Functions

The library provides the following functions for type detection:

• isArguments(value): boolean: whether the specified value is the JavaScript built-in arguments object, i.e., an array-like object representing the arguments passed to a function.
• isBigInt(value): boolean: whether the specified value is a JavaScript built-in bigint primitive.
• isBoolean(value): boolean: whether the specified value is a JavaScript built-in boolean primitive or Boolean object.
• isBuffer(value): boolean: whether the specified value is a JavaScript built-in ArrayBuffer or SharedArrayBuffer object.
• isBuiltInClass(Class): boolean: whether the specified class is a JavaScript built-in class.
• isCollection(value): boolean: whether the specified value is a JavaScript built-in collection object, i.e., a Map or Set object. Note that the WeakMap and WeakSet objects are not considered normal collection objects, and they can be detected by the isWeakCollection(value) function.
• isConsole(value): boolean: whether the specified value is a JavaScript built-in console object.
• isCssom(value): boolean: whether the specified value is a JavaScript built-in CSSOM object.
• isDataView(value): boolean: whether the specified value is a JavaScript built-in DataView object.
• isDom(value): boolean: whether the specified value is a JavaScript built-in DOM object.
• isError(value): boolean: whether the specified value is an instance of the JavaScript built-in Error class or its subclass.
• isEvent(value): boolean: whether the specified value is a JavaScript built-in event object, i.e., an instance of the JavaScript built-in Event class or its subclass.
• isFile(value): boolean: whether the specified value is a JavaScript File API object, i.e., an instance of the File, Blob, FileList, FileReader, or FileReaderSync class.
• isGlobalObject(value): boolean: whether the specified value is the global object.
• isIntl(value): boolean: whether the specified value is a JavaScript built-in object under the Intl namespace.
• isIterator(value): boolean: whether the specified value is an iterator object, i.e., an object with a next() method.
• isNumber(value): boolean: whether the specified value is a JavaScript built-in number primitive, or a Number object.
• isNumeric(value): boolean: whether the specified value is a JavaScript built-in number primitive, or bigint primitive, or Number object.
• isString(value): boolean: whether the specified value is a JavaScript built-in string primitive, or String object.
• isSymbol(value): boolean: whether the specified value is a JavaScript built-in Symbol primitive.
• isTypedArray(value): boolean: whether the specified value is a JavaScript built-in typed array object.
• isWeak(value): boolean: whether the specified value is a JavaScript built-in weak referenced object, i.e., a WeakMap, WeakSet, or WeakRef object.
• isWeakCollection(value): boolean: whether the specified value is a JavaScript built-in weak reference collection object, i.e., a WeakMap, or WeakSet object.

The following code shows how to use these functions:

import { isTypedArray } from '@haixing_hu/type-detect';

function foo(value) {
  if (isTypedArray(value)) {
    ...
  } else {
    ...
  }
}

Feature Detection Constants

This library provides the following constants for feature detection:

• AGGREGATEERROR_EXISTS: whether the JavaScript built-in class AggregateError exists.
• ARRAYBUFFER_EXISTS: whether the JavaScript built-in class ArrayBuffer exists.
• ARRAY_ISARRAY_EXISTS: whether the JavaScript built-in function Array.isArray() exists.
• ARRAY_ITERATOR_EXISTS: whether the JavaScript built-in function Array.prototype[Symbol.iterator] exists.
• ASYNC_FUNCTION_EXISTS: whether the JavaScript built-in async function exists.
• ATOMICS_EXISTS: whether the JavaScript built-in object Atomics exists.
• BIGINT64ARRAY_EXISTS: whether the JavaScript built-in class BigInt64Array exists.
• BIGINT_EXISTS: whether the JavaScript built-in primitive bigint and built-in function BigInt exists.
• BIGUINT64ARRAY_EXISTS: whether the JavaScript built-in class BigUint64Array exists.
• DATAVIEW_EXISTS: whether the JavaScript built-in class DataView exists.
• FINALIZATIONREGISTRY_EXISTS: whether the JavaScript built-in class FinalizationRegistry exists.
• FLOAT32ARRAY_EXISTS: whether the JavaScript built-in class Float32Array exists.
• FLOAT64ARRAY_EXISTS: whether the JavaScript built-in class Float64Array exists.
• INT16ARRAY_EXISTS: whether the JavaScript built-in class Int16Array exists.
• INT32ARRAY_EXISTS: whether the JavaScript built-in class Int32Array exists.
• INT8ARRAY_EXISTS: whether the JavaScript built-in class Int8Array exists.
• INTERNALERROR_EXISTS: whether the JavaScript built-in class InternalError class exists.
• INTL_COLLATOR_EXISTS: whether the JavaScript built-in class Intl.Collator class exists.
• INTL_DATETIMEFORMAT_EXISTS: whether the JavaScript built-in class Intl.DateTimeFormat class exists.
• INTL_DISPLAYNAMES_EXISTS: whether the JavaScript built-in class Intl.DisplayNames class exists.
• INTL_DURATIONFORMAT_EXISTS: whether the JavaScript built-in class Intl.DurationFormat class exists.
• INTL_EXISTS: whether the JavaScript built-in Intl namespace exists.
• INTL_LISTFORMAT_EXISTS: whether the JavaScript built-in class Intl.ListFormat exists.
• INTL_LOCALE_EXISTS: whether the JavaScript built-in class Intl.Locale exists.
• INTL_NUMBERFORMAT_EXISTS: whether the JavaScript built-in class Intl.NumberFormat exists.
• INTL_PLURALRULES_EXISTS: whether the JavaScript built-in class Intl.PluralRules exists.
• INTL_RELATIVETIMEFORMAT_EXISTS: whether the JavaScript built-in class Intl.RelativeTimeFormat exists.
• INTL_SEGMENTER_EXISTS: whether the JavaScript built-in class Intl.Segmenter exists.
• INTL_SEGMENTER_ITERATOR_EXISTS: whether the JavaScript built-in function Intl.Segmenter.prototype[Symbol.iterator] exists.
• MAP_ENTRIES_EXISTS: whether the JavaScript built-in function Map.prototype.entries() exists.
• MAP_EXISTS: whether the JavaScript built-in class Map exists.
• MAP_ITERATOR_EXISTS: whether the JavaScript built-in function Map.prototype[Symbol.iterator] exists.
• PROMISE_EXISTS: whether the JavaScript built-in class Promise exists.
• PROXY_EXISTS: whether the JavaScript built-in class Proxy exists.
• REFLECT_EXISTS: whether the JavaScript built-in namespace Reflect exists.
• REGEXP_EXISTS: whether the JavaScript built-in class RegExp exists.
• REGEXP_ITERATOR_EXISTS: whether the JavaScript built-in function RegExp.prototype[Symbol.matchAll] exists.
• SET_ENTRIES_EXISTS: whether the JavaScript built-in function Set.prototype.entries() exists.
• SET_EXISTS: whether the JavaScript built-in class Set exists.
• SET_ITERATOR_EXISTS: whether the JavaScript built-in function Set.prototype[Symbol.iterator] exists.
• SHAREDARRAYBUFFER_EXISTS: whether the JavaScript built-in class SharedArrayBuffer exists.
• STRING_ITERATOR_EXISTS: whether the JavaScript built-in function String.prototype[Symbol.iterator] exists.
• SYMBOL_EXISTS: whether the JavaScript built-in Symbol exists.
• SYMBOL_ITERATOR_EXISTS: whether the JavaScript built-in function Symbol.prototype[Symbol.iterator] exists.
• SYMBOL_MATCH_ALL_EXISTS: whether the JavaScript built-in function Symbol.prototype[Symbol.matchAll] exists.
• SYMBOL_TO_STRING_TAG_EXISTS: whether the JavaScript built-in function Symbol.prototype[Symbol.toStringTag] exists.
• UINT16ARRAY_EXISTS: whether the JavaScript built-in class Uint16Array exists.
• UINT32ARRAY_EXISTS: whether the JavaScript built-in class Uint32Array exists.
• UINT8ARRAY_EXISTS: whether the JavaScript built-in class Uint8Array exists.
• UINT8CLAMPEDARRAY_EXISTS: whether the JavaScript built-in class Uint8ClampedArray exists.
• WEAKMAP_EXISTS: whether the JavaScript built-in class WeakMap exists.
• WEAKREF_EXISTS: whether the JavaScript built-in class WeakRef exists.
• WEAKSET_EXISTS: whether the JavaScript built-in class WeakSet exists.

The following code shows how to use these constants:

import { WEAKMAP_EXISTS } from '@haixing_hu/type-detect';

function foo(value) {
  if (WEAKMAP_EXISTS) {
    ...
  } else {
    ...
  }
}

Type Prototype Constants

This library provides the following constants for the prototypes of JavaScript built-in objects:

• AggregateErrorPrototype: the prototype of the JavaScript built-in AggregateError objects, or undefined if the AggregateError class does not exist.
• ArrayBufferPrototype: the prototype of the JavaScript built-in ArrayBuffer objects, or undefined if the ArrayBuffer class does not exist.
• ArrayIteratorPrototype: the prototype of the JavaScript built-in array iterator objects, or undefined if the array iterator does not exist.
• BigInt64ArrayPrototype: the prototype of the JavaScript built-in BigInt64Array objects, or undefined if the BigInt64Array class does not exist.
• BigIntPrototype: the prototype of the JavaScript built-in bigint primitive, or undefined if the bigint primitive does not exist.
• BigUint64ArrayPrototype: the prototype of the JavaScript built-in BigUint64Array objects, or undefined if the BigUint64Array class does not exist.
• DataViewPrototype: the prototype of the JavaScript built-in DataView objects, or undefined if the DataView class does not exist.
• FinalizationRegistryPrototype: the prototype of the JavaScript built-in FinalizationRegistry objects, or undefined if the FinalizationRegistry class does not exist.
• Float32ArrayPrototype: the prototype of the JavaScript built-in Float32Array objects, or undefined if the Float32Array class does not exist.
• Float64ArrayPrototype: the prototype of the JavaScript built-in Float64Array objects, or undefined if the Float64Array class does not exist.
• Int16ArrayPrototype: the prototype of the JavaScript built-in Int16Array objects, or undefined if the Int16Array class does not exist.
• Int32ArrayPrototype: the prototype of the JavaScript built-in Int32Array objects, or undefined if the Int32Array class does not exist.
• Int8ArrayPrototype: the prototype of the JavaScript built-in Int8Array objects, or undefined if the Int8Array class does not exist.
• IntelSegmentIteratorPrototype: the prototype of the JavaScript built-in Intl.SegmentIterator objects, or undefined if the Intl.SegmentIterator class does not exist.
• InternalErrorPrototype: the prototype of the JavaScript built-in InternalError objects, or undefined if the InternalError class does not exist.
• IntlCollatorPrototype: the prototype of the JavaScript built-in Intl.Collator objects, or undefined if the Intl.Collator class does not exist.
• IntlDateTimeFormatPrototype: the prototype of the JavaScript built-in Intl.DateTimeFormat objects, or undefined if the Intl.DateTimeFormat class does not exist.
• IntlDisplayNamesPrototype: the prototype of the JavaScript built-in Intl.DisplayNames objects, or undefined if the Intl.DisplayNames class does not exist.
• IntlDurationFormatPrototype: the prototype of the JavaScript built-in Intl.DurationFormat objects, or undefined if the Intl.DurationFormat class does not exist.
• IntlListFormatPrototype: the prototype of the JavaScript built-in Intl.ListFormat objects, or undefined if the Intl.ListFormat class does not exist.
• IntlLocalePrototype: the prototype of the JavaScript built-in Intl.Locale objects, or undefined if the Intl.Locale class does not exist.
• IntlNumberFormatPrototype: the prototype of the JavaScript built-in Intl.NumberFormat objects, or undefined if the Intl.NumberFormat class does not exist.
• IntlPluralRulesPrototype: the prototype of the JavaScript built-in Intl.PluralRules objects, or undefined if the Intl.PluralRules class does not exist.
• IntlRelativeTimeFormatPrototype: the prototype of the JavaScript built-in Intl.RelativeTimeFormat objects, or undefined if the Intl.RelativeTimeFormat class does not exist.
• IntlSegmenterPrototype: the prototype of the JavaScript built-in Intl.Segmenter objects, or undefined if the Intl.Segmenter class does not exist.
• MapIteratorPrototype: the prototype of the JavaScript built-in Map iterator objects, or undefined if the Map iterator does not exist.
• MapPrototype: the prototype of the JavaScript built-in Map objects, or undefined if the Map class does not exist.
• PromisePrototype: the prototype of the JavaScript built-in Promise objects, or undefined if the Promise class does not exist.
• RegExpIteratorPrototype: the prototype of the JavaScript built-in RegExp iterator objects, or undefined if the RegExp iterator does not exist.
• RegExpPrototype: the prototype of the JavaScript built-in RegExp objects, or undefined if the RegExp class does not exist.
• SetIteratorPrototype: the prototype of the JavaScript built-in Set iterator objects, or undefined if the Set iterator does not exist.
• SetPrototype: the prototype of the JavaScript built-in Set objects, or undefined if the Set class does not exist.
• SharedArrayBufferPrototype: the prototype of the JavaScript built-in SharedArrayBuffer objects, or undefined if the SharedArrayBuffer class does not exist.
• StringIteratorPrototype: the prototype of the JavaScript built-in String iterator objects, or undefined if the String iterator does not exist.
• SymbolPrototype: the prototype of the JavaScript built-in Symbol primitives, or undefined if the Symbol primitive does not exist.
• Uint16ArrayPrototype: the prototype of the JavaScript built-in Uint16Array objects, or undefined if the Uint16Array class does not exist.
• Uint32ArrayPrototype: the prototype of the JavaScript built-in Uint32Array objects, or undefined if the Uint32Array class does not exist.
• Uint8ArrayPrototype: the prototype of the JavaScript built-in Uint8Array objects, or undefined if the Uint8Array class does not exist.
• Uint8ClampedArrayPrototype: the prototype of the JavaScript built-in Uint8ClampedArray objects, or undefined if the Uint8ClampedArray class does not exist.
• WeakMapPrototype: the prototype of the JavaScript built-in WeakMap objects, or undefined if the WeakMap class does not exist.
• WeakRefPrototype: the prototype of the JavaScript built-in WeakRef objects, or undefined if the WeakRef class does not exist.
• WeakSetPrototype: the prototype of the JavaScript built-in WeakSet objects, or undefined if the WeakSet class does not exist.

The following code shows how to use these constants:

import { WeakMapPrototype } from '@haixing_hu/type-detect';

function foo(value) {
  const proto = Object.getPrototypeOf(value);
  if (proto === WeakMapPrototype) {
    ...
  } else {
    ...
  }
}

Why Proxy Type Cannot be Detected

One of the primary purposes of Proxy objects in JavaScript is to allow developers to customize the behavior of object operations, acting as a delegate for another object (referred to as the target object). One of the key features of Proxy is its transparency—externally, unless the proxy object is intentionally designed to reveal itself, it is challenging to distinguish a Proxy object from the target object it represents. This is largely because Proxy can intercept and redefine almost all fundamental operations of an object, including but not limited to property access, assignment, and enumeration.

Therefore, when libraries like type-detect attempt to retrieve type information of an object, the inherent transparency of Proxy means these libraries can only process and "see" the final outcomes of operations, without direct means to identify whether these operations were intercepted by a Proxy. If a Proxy flawlessly mimics the behavior of its target object, there exists no reliable method to determine from the operation outcomes whether an object is a Proxy. In essence, the design philosophy of Proxy aims to make it nearly invisible to external observation, making it impossible for even libraries specialized in fetching type information to definitively ascertain if an object is a Proxy, unless the proxy object deliberately exposes its identity through certain intercepting behaviors. This design significantly enhances the power and flexibility of Proxy, but it also means that directly detecting Proxy objects through external observation presents a challenge.

Contributing

If you find any issues or have suggestions for improvements, please feel free to open an issue or submit a pull request to the GitHub repository.

License

type-detect is distributed under the Apache 2.0 license. See the LICENSE file for more details.