typeof anything

Ecmascript can be a bitch when it comes to (determining) the type of variables. Sometimes typeof/instanceof/constructor etc. will just not give the right results. On the other hand I don't want to abandon dynamic typing, it offers that much more than static typing (so, no typescript here). But still, there are moments where I want to be more certain that a variable is of the type I actually need (e.g in my JQL library).

So I created this little module/library. It tries to provide a function to determine a type of anything your throw at it.

The code is available as an (importable) module, as a browser script and from NPM.

Import the module

Your script should be of type module.

<script type="module">
  import IS from "https://kooiinc.github.io/typeofAnything/typeofany.module.js";
  // or 
  const IS = (await import("https://kooiinc.github.io/typeofAnything/typeofany.module.js")).default;
</script>

Use in browser

Create a script tag in your html:

<script src="https://kooiinc.github.io/typeofAnything/typeofany.browser.js"`)</script>

Subsequently use window.IS in your script

<script>
  const IS = window.IS;
  // remove from global namespace
  delete window.IS;
  // ...
</script>

Syntax

[imported IS function](anything, [...type])

Return value

The method returns either a boolean (anything is/is not (one of) [...type]) or a string representation of the found 'type' (may also be null, NaN or undefined).

For checking if anything is (one of) [...type], the level of specificity is up to the prototype of anything (when it is found). For example

• IS(document.createElement("div"), HTMLDivElement) and IS(document.createElement("div"), HTMLElement) are both true, but IS(document.createElement("div"), Node) will be false.
• IS(Array, Object) will be false, IS(Array, Array) true.

Examples

// assume the function is imported as IS
const showMeMyType = something => IS(something)
const someObj = {a: 1, b: `hello`, c: `world`};
const wMap = new WeakMap();
IS(someObj); // => Object
showMeMyType(wMap); // => WeakMap
IS(someObj, Object); // => true
IS(someObj, Array, String); // => false
IS(someObj, Symbol, String, RegExp, Object); // => true
IS(null); //=> null
IS(null, undefined); //=> false
IS(null, null); //=> true
IS(/[a-z]/gi, RegExp); //=> true

For a more comprehensive example see this [Stackblitz project).