Nothing

Nothing is a chainable, callable mock object which always returns itself. You can use it instead of null and undefined values so you don't have to place safety checks all over your code. The implementation uses Symbol and Proxy behind the hood so your environment has to support it.

How to install

npm i -S nothing-mock

How to use

Property accessors

import {Nothing} from 'nothing-mock'

function executeActionWithNullChecks(context) {
	return context &&
		context.namespace &&
		context.namespace.actions &&
		context.namespace.actions.someAction &&
		context.namespace.actions.someAction()
}

// no need to check for null/undefined
function executeAction(context) {
	return context.namespace.actions.someAction()
}

executeActionWithNullChecks(null) // returns null
executeAction(Nothing) // returns Nothing
executeAction(null) // throws an exception

JSON serialization/deserialization

import {Nothing, deserialize, serialize} from 'nothing-mock'

const json = `{
	"posts": [{
		"id": 1,
		"userId": 12,
		"content": "post 1",
		"comments": [{
			"id": 1,
			"userId": 34,
			"content": "comment 1"
		}, {
			"id": 2,
			"userId": 56,
			"content": "comment 2"
		}]
	}, {
		"id": 2,
		"userId": 78,
		"content": "post 2",
		"comments": null
	}]
}`

const {posts} = deserialize(json) /* returns: [{
	"id": 1,
	"userId": 12,
	"content": "post 1",
	"comments": [{
		"id": 1,
		"userId": 34,
		"content": "comment 1"
	}, {
		"id": 2,
		"userId": 56,
		"content": "comment 2"
	}]
}, {
	"id": 2,
	"userId": 78,
	"content": "post 2",
	"comments": Nothing // null values are replaced with Nothing
}] */

function renderPostWithComments(post) {
	return `<div>
		<p>${post.content}</p>
		<ul>${post.comments.map((comment) =>
			`<li>${comment.content}</li>`).join('')
		}</ul>
	</div>`
}

posts.map(renderPostWithComments).join('') /* returns:
`<div>
	<p>post 1</p>
	<ul>
		<li>comment 1</li>
		<li>comment 2</li>
	</ul>
</div>
<div>
	<p>post 2</p>
	<ul></ul> // Nothing is rendered empty
</div>` */

serialize({posts}) // changes all Nothing values to null

Filtering and helpers

import {Nothing, toBool, isNothing, isSomething} from 'nothing-mock'

const list = [Nothing, true, false, null, undefined, 0, 1, NaN, '', {}, []]
list.filter(Boolean) // [Nothing, true, 1, {}, []]
list.filter(isNaN) // [undefined, NaN, {}]
list.filter(isNothing) // [Nothing]
list.filter(isSomething) // [true, false, 0, 1, NaN, "", {}, []]
list.filter(Number) // [true, 1]
list.filter(String) // [true, false, null, undefined, 0, 1, NaN, {}]
list.filter(toBool) // [true, 1, {}, []]

A list of properties which don't return Nothing

import {Nothing} from 'nothing-mock'

Nothing.length // 0
Nothing.name // a string
Nothing.prototype // an object with a constructor
Nothing.toLocaleString() // ""
Nothing.toString() // ""
Nothing.valueOf() // false

Typecasting and gotchas

import {Nothing, toBool} from 'nothing-mock'

String(Nothing) // ""
Nothing.toString() // ""
Nothing + 'a string' // "a string"
Nothing * 123 // 0
Nothing - 123 // -123

// Gotcha: concatenation of Nothing and a number returns a string
Nothing + 123 // "123"

// Solution: Nothing can be excplicitly converted to a number
Number(Nothing) // 0
Number(Nothing) + 123 // 123

// Gotcha: typecasting of Nothing to a boolean returns true
Boolean(Nothing) // true
!!Nothing // true

// Solution: Nothing can be properly converted to a falsy value
Nothing.valueOf() // false
toBool(Nothing) // false
toBool(undefined) // false
toBool(123) // true

// Gotcha: returning Nothing from a promise never resolves as Nothing is
// a thenable object
somePromise
	.then(() => Nothing)
	.then((result) => result) // pending indefinitely

// Solution: wrapping of Nothing into an object resolves successfully
somePromise
	.then(() => ({result: Nothing}))
	.then((result) => result) // promise resolves

License

MIT