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

type-detect

Improved typeof detection for node.js and the browser.

Installation

Node.js

type-detect is available on npm.

$ npm install type-detect

Component

type-detect is available as a component.

$ component install chaijs/type-detect

Usage

Primary

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

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

array

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

regexp

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

function

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

arguments

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

date

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

number

assert('number' === type(1));
assert('number' === type(1.234));
assert('number' === type(-1));
assert('number' === type(-1.234));
assert('number' === type(Infinity));
assert('number' === type(NaN));

string

assert('string' === type('hello world'));

null

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

undefined

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

object

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

Library

A Library is a small constructed repository for custom type detections.

var lib = new type.Library;

.of (obj)

• @param {Mixed} object to test
• @return {String} type

Expose replacement typeof detection to the library.

if ('string' === lib.of('hello world')) {
  // ...
}

.define (type, test)

• @param {String} type
• @param {RegExp|Function} test

Add a test to for the .test() assertion.

Can be defined as a regular expression:

lib.define('int', /^[0-9]+$/);

... or as a function:

lib.define('bln', function (obj) {
  if ('boolean' === lib.of(obj)) return true;
  var blns = [ 'yes', 'no', 'true', 'false', 1, 0 ];
  if ('string' === lib.of(obj)) obj = obj.toLowerCase();
  return !! ~blns.indexOf(obj);
});

.test (obj, test)

• @param {Mixed} object
• @param {String} type
• @return {Boolean} result

Assert that an object is of type. Will first check natives, and if that does not pass it will use the user defined custom tests.

assert(lib.test('1', 'int'));
assert(lib.test('yes', 'bln'));

License

(The MIT License)

Copyright (c) 2013 Jake Luer [e-mail] (http://alogicalparadox.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.