type-detect

What is type-detect?

The type-detect npm package is a utility for accurately detecting the types of JavaScript values. It goes beyond the basic `typeof` operator by being able to distinguish between more specific types, such as differentiating between an array and an object, or identifying specific types of objects like Date, RegExp, etc. This can be particularly useful in situations where strict type checking is necessary, such as input validation, or when working with complex data structures.

What are type-detect's main functionalities?

Detecting basic JavaScript types

This feature allows for the detection of basic JavaScript types such as number, boolean, string, null, and undefined. It provides a more reliable method than the `typeof` operator for these types.

"use strict";\nconst typeDetect = require('type-detect');\nconsole.log(typeDetect(1)); // 'number'\nconsole.log(typeDetect(true)); // 'boolean'\nconsole.log(typeDetect('Hello')); // 'string'\nconsole.log(typeDetect(null)); // 'null'\nconsole.log(typeDetect(undefined)); // 'undefined'

Distinguishing between arrays, objects, and null

This feature showcases the ability of type-detect to accurately distinguish between arrays, plain objects, and null, which is a common source of confusion when using the `typeof` operator.

"use strict";\nconst typeDetect = require('type-detect');\nconsole.log(typeDetect([])); // 'Array'\nconsole.log(typeDetect({})); // 'Object'\nconsole.log(typeDetect(null)); // 'null'

Identifying complex built-in types

This demonstrates type-detect's capability to identify more complex built-in JavaScript types such as Date objects and RegExp objects, which are not distinguishable using `typeof`.

"use strict";\nconst typeDetect = require('type-detect');\nconsole.log(typeDetect(new Date())); // 'Date'\nconsole.log(typeDetect(/regex/)); // 'RegExp'

Other packages similar to type-detect

is

The 'is' package provides a comprehensive set of type-check functions, similar to type-detect. It includes checks for primitive types, built-in objects, and also offers functions to test for specific conditions (like whether a number is integer). Compared to type-detect, 'is' might offer a more function-oriented approach for type checking.

check-types

The 'check-types' package offers a similar functionality to type-detect, focusing on providing a large set of assertion functions to validate the types of variables. It supports a wide range of types and conditions, including checks for truthy or falsy values. 'check-types' might be preferred in scenarios where assertions are more suitable than simple type detection.

README

Improved typeof detection for node, Deno, and the browser.

Supported Browsers
Chrome	Edge	Firefox	Safari	IE
✅	✅	✅	✅	9, 10, 11

What is Type-Detect?

Type Detect is a module which you can use to detect the type of a given object. It returns a string representation of the object's type, either using typeof or @@toStringTag. It also normalizes some object names for consistency among browsers.

Why?

The typeof operator will only specify primitive values; everything else is "object" (including null, arrays, regexps, etc). Many developers use Object.prototype.toString() - which is a fine alternative and returns many more types (null returns [object Null], Arrays as [object Array], regexps as [object RegExp] etc).

Sadly, Object.prototype.toString is slow, and buggy. By slow - we mean it is slower than typeof. By buggy - we mean that some values (like Promises, the global object, iterators, dataviews, a bunch of HTML elements) all report different things in different browsers.

type-detect fixes all of the shortcomings with Object.prototype.toString. We have extra code to speed up checks of JS and DOM objects, as much as 20-30x faster for some values. type-detect also fixes any consistencies with these objects.

Installation

Node.js

type-detect is available on npm. To install it, type:

$ npm install type-detect

Deno

type-detect can be imported with the following line:

import type from 'https://deno.land/x/type_detect@v4.1.0/index.ts'

Browsers

You can also use it within the browser; install via npm and use the type-detect.js file found within the download. For example:

<script src="./node_modules/type-detect/type-detect.js"></script>

Usage

The primary export of type-detect is function that can serve as a replacement for typeof. The results of this function will be more specific than that of native typeof.

var type = require('type-detect');

Or, in the browser use case, after the

var type = typeDetect;

array

assert(type([]) === 'Array');
assert(type(new Array()) === 'Array');

regexp

assert(type(/a-z/gi) === 'RegExp');
assert(type(new RegExp('a-z')) === 'RegExp');

function

assert(type(function () {}) === 'function');

arguments

(function () {
  assert(type(arguments) === 'Arguments');
})();

date

assert(type(new Date) === 'Date');

number

assert(type(1) === 'number');
assert(type(1.234) === 'number');
assert(type(-1) === 'number');
assert(type(-1.234) === 'number');
assert(type(Infinity) === 'number');
assert(type(NaN) === 'number');
assert(type(new Number(1)) === 'Number'); // note - the object version has a capital N

string

assert(type('hello world') === 'string');
assert(type(new String('hello')) === 'String'); // note - the object version has a capital S

null

assert(type(null) === 'null');
assert(type(undefined) !== 'null');

undefined

assert(type(undefined) === 'undefined');
assert(type(null) !== 'undefined');

object

var Noop = function () {};
assert(type({}) === 'Object');
assert(type(Noop) !== 'Object');
assert(type(new Noop) === 'Object');
assert(type(new Object) === 'Object');

ECMA6 Types

All new ECMAScript 2015 objects are also supported, such as Promises and Symbols:

assert(type(new Map() === 'Map');
assert(type(new WeakMap()) === 'WeakMap');
assert(type(new Set()) === 'Set');
assert(type(new WeakSet()) === 'WeakSet');
assert(type(Symbol()) === 'symbol');
assert(type(new Promise(callback) === 'Promise');
assert(type(new Int8Array()) === 'Int8Array');
assert(type(new Uint8Array()) === 'Uint8Array');
assert(type(new UInt8ClampedArray()) === 'Uint8ClampedArray');
assert(type(new Int16Array()) === 'Int16Array');
assert(type(new Uint16Array()) === 'Uint16Array');
assert(type(new Int32Array()) === 'Int32Array');
assert(type(new UInt32Array()) === 'Uint32Array');
assert(type(new Float32Array()) === 'Float32Array');
assert(type(new Float64Array()) === 'Float64Array');
assert(type(new ArrayBuffer()) === 'ArrayBuffer');
assert(type(new DataView(arrayBuffer)) === 'DataView');

Also, if you use Symbol.toStringTag to change an Objects return value of the toString() Method, type() will return this value, e.g:

var myObject = {};
myObject[Symbol.toStringTag] = 'myCustomType';
assert(type(myObject) === 'myCustomType');