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https://github.com/slmgc/Nothing
A chainable, callable mock object which always returns itself
https://github.com/slmgc/Nothing
callable chainable mock nothing testing
Last synced: about 2 months ago
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A chainable, callable mock object which always returns itself
- Host: GitHub
- URL: https://github.com/slmgc/Nothing
- Owner: slmgc
- License: mit
- Created: 2017-05-22T17:17:52.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2023-10-17T03:00:28.000Z (about 1 year ago)
- Last Synced: 2024-10-26T13:11:22.836Z (2 months ago)
- Topics: callable, chainable, mock, nothing, testing
- Language: JavaScript
- Homepage:
- Size: 555 KB
- Stars: 363
- Watchers: 5
- Forks: 7
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Nothing
[![npm package][npm-badge]][npm] [![npm package][npm-downloads]][npm]
**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 which are widely supported by modern desktop and mobile browsers and can be used without a polyfill.
## How to install
```
npm i -S nothing-mock
```
## How to use
### A simple example
```js
import {Nothing} from 'nothing-mock'
const foo = Nothing
foo.bar.baz.qux().spam.ham[0].map((x) => x + 1).eggs.someFn() // returns Nothing
```
### Reducing boilerplate
```js
import {Nothing} from 'nothing-mock'
// A regular function with null-checks
function someFunctionWithNullChecks(foo) {
return foo &&
foo.bar &&
foo.bar.baz &&
foo.bar.baz.qux &&
foo.bar.baz.qux()
}
// There is no need to check for null/undefined if you use Nothing
function someFunction(foo) {
return foo.bar.baz.qux()
}
someFunctionWithNullChecks(null) // returns null
someFunction(Nothing) // returns Nothing
someFunction(null) // throws an exception
```
### JSON serialization/deserialization
```js
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 `
${post.content}
${post.comments.map((comment) =>
`- ${comment.content}
`).join('')
}
`
}
posts.map(renderPostWithComments).join('') /* returns:
`
post 1
- comment 1
- comment 2
post 2
// Nothing is rendered empty
` */
// Serializes an object to JSON and
// replaces all Nothing values with null
serialize({posts})
```
### Helper functions
```js
import {Nothing, toBool, isNothing, isSomething} from 'nothing-mock'
const list = [Nothing, true, false, null, undefined, 0, 1, NaN, '', {}, []]
list.filter(toBool) // [true, 1, {}, []]
list.filter(isNothing) // [Nothing]
list.filter(isSomething) // [true, false, 0, 1, NaN, "", {}, []]
```
### Properties which don't return Nothing
```jsx
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
```
### Gotchas
```js
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 converted to false
Nothing.valueOf() // false
toBool(Nothing) // false
// Gotcha: returning Nothing from a promise never
// resolves as Nothing is a thenable object
somePromise
.then(() => Nothing)
.then((result) => result) // pending indefinitely
// Solution: wrapping Nothing resolves the issue
somePromise
.then(() => ({result: Nothing}))
.then((result) => result) // promise resolves
```
## FAQ
Q-1: Proxies are slow and there is a runtime overhead. Why should I use **Nothing**?
A: You should keep a few things in mind:
1. "Premature optimization is the root of all evil" - Donald E. Knuth.
2. Have you checked the performance of **Nothing**? Does it really impact the performance of your code? If it does, you can always opt out using **Nothing** for performance-critical parts of your code.
3. You can use **Nothing** for writing unit tests which are less likely to be performance-dependant.
Q-2: I believe that it's hard to understand the logic as the code will fail silently if I would use **Nothing**. I prefer to use try/catch blocks instead, e.g.:
```js
try {
foo.bar.baz()
} catch (e) {
// deal with it somehow
}
```
A: Many functional programming languages either don't have or don't endorse the use of imperative constructs such as try/catch blocks because they introduce so-called side effects which actually make it harder to debug and reason about the code. And programs which are written in functional programming languages are considered to be less error-prone and easier to support.
You can always check the result if a function call should never return **Nothing** and then handle it properly:
```js
const someFunction = (handleNothing, arg) => {
const result = foo.bar.baz(arg)
return isNothing(result) ? handleNothing(arg) : result
}
```
Q-3: Why should I use **Nothing** if there are better alternatives like [optional chaining] or [lodash.get]?
A: Each of these solutions have their pros and cons. Your choice should depend on the use-case:
1. Optional chaining syntax would be the best choice, but it requires a transpilation step as modern browsers don't support the syntax and it might take a while before it will get into the future ECMAScript standard.
2. `lodash.get` is good for a basic property chain traversal, but it requires an alien syntax and fails when there is a need to call a method somewhere in a property chain:
```js
import get from 'lodash.get'
var foo = null
get(foo, ['bar', 'baz'])() // this will throw an exception
var baz = get(foo, ['bar', 'baz'])
baz && baz() // this won't work if `baz` should be bound to the context of `bar`
// For example:
var foo = {
bar: {
baz() {
console.log(this.qux)
},
qux: 'hello'
}
}
foo.bar.baz() // "hello"
get(foo, ['bar', 'baz'])() // undefined
// This would be a proper solution:
var bar = get(foo, ['bar'])
var baz = get(bar, ['baz'])
baz && baz.call(bar) // "hello"
// But then it's easier to get back to the regular syntax:
foo && foo.bar && foo.bar.baz && foo.bar.baz()
// And good luck using `get` for something like this:
foo.bar.baz()[0].map(() => { /* do something */ })
// BTW, an implementation of a lodash-like `get` helper-function is basically a one-liner:
const get = (o, a) => a.reduce((p, c) => p && p[c], o)
```
Q-4: I am still not convinced and ain't gonna use **Nothing**!
A: Thanks for letting me know! Seriously, it's your choice, I am down with it.
## License
**MIT**
[Proxy]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy#Browser_compatibility
[Symbol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol#Browser_compatibility
[npm]: https://www.npmjs.org/package/nothing-mock
[npm-badge]: https://img.shields.io/npm/v/nothing-mock.svg
[npm-downloads]: https://img.shields.io/npm/dm/nothing-mock.svg
[optional chaining]: https://www.npmjs.com/package/babel-plugin-transform-optional-chaining
[lodash.get]: https://www.npmjs.com/package/lodash.get