@stdlib/utils/type-of/lib/main.js

Standard utilities.

/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var ctorName = require( './../../constructor-name' );


// NOTES //

/*
* Built-in `typeof` operator behavior:
*
* ```text
* typeof null => 'object'
* typeof undefined => 'undefined'
* typeof 'a' => 'string'
* typeof 5 => 'number'
* typeof NaN => 'number'
* typeof true => 'boolean'
* typeof false => 'boolean'
* typeof {} => 'object'
* typeof [] => 'object'
* typeof function foo(){} => 'function'
* typeof function* foo(){} => 'object'
* typeof Symbol() => 'symbol'
* ```
*
*/


// MAIN //

/**
* Determines a value's type.
*
* @param {*} v - input value
* @returns {string} string indicating the value's type
*/
function typeOf( v ) {
	var type;

	// Address `typeof null` => `object` (see http://wiki.ecmascript.org/doku.php?id=harmony:typeof_null):
	if ( v === null ) {
		return 'null';
	}
	type = typeof v;

	// If the `typeof` operator returned something other than `object`, we are done. Otherwise, we need to check for an internal class name or search for a constructor.
	if ( type === 'object' ) {
		return ctorName( v ).toLowerCase();
	}
	return type;
}


// EXPORTS //

module.exports = typeOf;