Package Exports
- kindof
This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (kindof) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.
Readme
Kindof.js
Kindof.js provides the kindof function that does what you'd expect from typeof — gives you the proper semantic type regardless if the variable was a primitive literal ("Hello"), a boxed object (new String("Hello")) or came from another execution context (e.g. an array from another <iframe>).
Kindof.js supports all ECMAScript built-in types and classes: undefined, null, Boolean, Number, String, RegExp, Date, Array, Function and plain old Object. Others, e.g. Math and JSON, are considered just objects. In general, objects that behave like value objects (numbers, dates etc.) or proper arrays have a kind other than object.
Please see the table below for the full list of kinds.
Using
Note: Kindof.js follows semantic versioning.
Installing for the browser
Take the index.js file, rename it how you'd like and source it at will.
Installing on Node
Install with npm install kindof.
And require with var kindof = require("kindof").
Using
Then continue as you would:
kindof("Hello") // => "string"
kindof(new String("Hello")) // => "string"Kinds
The pattern is simple — all built-in objects that behave like value objects (numbers, strings, dates etc.) or are real arrays are said to be of a kind other than object. The arguments object, however, is not a proper array, so it therefore is an object.
| Value | Kindof |
|---|---|
undefined |
undefined |
null |
null |
true |
boolean |
false |
boolean |
new Boolean(true) |
boolean |
42 |
number |
new Number(42) |
number |
NaN |
number |
Infinity |
number |
"Hello" |
string |
new String("Hello") |
string |
/.*/ |
regexp |
new RegExp(".*") |
regexp |
new Date |
date |
[42, 69] |
array |
function() {} |
function |
{} |
object |
arguments |
object |
new MyClass |
object |
new Error |
object |
Math |
object |
JSON |
object |
Subclassed objects, such as subclassed arrays, are considered to be object unless their internal [[Class]] property remains Array. For ways to subclass properly, please see further reading below.
Further Reading
- The
typeofoperator in ECMAScript 5.1. - The
typeofoperator as implemented by Firefox. - Article on subclassing
Arrayby Juriy Zaytsev.
License
Kindof.js is released under a Lesser GNU Affero General Public License, which in summary means:
- You can use this program for no cost.
- You can use this program for both personal and commercial reasons.
- You do not have to share your own program's code which uses this program.
- You have to share modifications (e.g bug-fixes) you've made to this program.
For more convoluted language, see the LICENSE file.
About
Andri Möll typed this and the code.
Monday Calendar supported the engineering work.
If you find Kindof.js needs improving, please don't hesitate to type to me now at andri@dot.ee or create an issue online.