is.js

$ npm i @schwingbat/is

Type checking in JS is stupid. is is also stupid, but it's more fun.

Check it:

var object = {
  value: "Hello, I'm an object"
}

var array = ["Hello", "I'm", "an", "array"]

is.object(object) // returns true
is.object(array) // returns false
is.array(array) // returns true
is.number('not a number') // returns false

// You can also use is.what() like typeof for built-in types instead of checking against a specific type

is.what(object) // returns 'object'
is.what(array) // returns 'array'
is.what(12345) // returns 'number'
is.what('what is this?') // returns 'string'

JavaScript's type annoyances are still there, but they're abstracted away where you don't have to care that they exist. is in an object with a couple of built in properties. One of these is a function called define which you can use to define your own 'types'. For example, that is.object function above is implemented like this:

is.define('object', function(val) {
  return typeof val === 'object'
    && !Array.isArray(val)
    && val !== null
})

It's super simple. You could write is yourself in a few minutes. Fortunately, I already did. is comes with all the basic types predefined, but you can also define whatever else you might find useful:

is.define('vector3', function(val) {
  return is.array(val) && val.length === 3
})

var possibleVector3 = [25.3, 17, 992]

// Then just use it like this:
is.vector3(possibleVector3) // returns true!

...or even...

is.define('is', function(val) {
  return val.hasOwnProperty('define') && is.func(val.define)
})

is.is(is) // indeed

It basically goes on like that. That's pretty much all there is to it. You can use is to validate pretty much anything you want because you can use functions to validate pretty much anything you want. is just groups them together and makes them look nice. Check out the is.js file for the full list of included types.

Instances

Depending on your program, you might find you want to have multiple copies of is with their own separate definitions. An example in node might look like this:

var is = require('@schwingbat/is').instance()
var is2 = require('@schwingbat/is').instance()

is.define('hexColor', function(val) {
  return is.string(val) && val.length === 7 && val[0] === '#'
})

is.hexColor('#ff0088') // true
is2.hexColor('#ff0088') // TypeError: is.hexColor is not a function

You can define as many properties as you want on an instance and it won't pollute the global copy of is. In fact, if you wanted to you could nest instances inside the global is:

is.color = is.instance()

is.color.define('hex', function(val) {
  return is.string(val) && val.length === 7 && val[0] === '#'
})

is.color.define('rgb', function(val) {
  return is.object(val) && val.r && val.g && val.b
})

is.color.hex('#ffffff') // true
is.color.rgb({ r: 128, g: 62, b: 232 }) // true

But I digress. Set it up however you want, or just use it out of the box. Hopefully you find it useful. Require it in Node, use a script tag in HTML. It should work just about anywhere. Have fun!