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js-equality-game

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The Worst Minesweeper 💣 Ever

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<h1 align="center">
  <a href="https://eqeq.js.org/"><img src="https://raw.githubusercontent.com/slikts/js-equality-game/assets/logo.svg?sanitize=true" width="300" alt="JavaScript Equality Table Game"></a>
</h1>
<p align="center">…or why you should prefer the <code>===</code> operator.</p>

---

[![Build Status](https://travis-ci.org/slikts/js-equality-game.svg?branch=master)](https://travis-ci.org/slikts/js-equality-game)

- [**Play the game**][game]
- Inspired by [JavaScript Equality Table][table]
- [Discussion about value order][reorder]
- [Weak typing][wikipedia] in Wikipedia
- [Visual explanation][visual]
- [Abstract equality comparison rules][abstract-rules] in ECMA-262

## Screenshot

[![Screenshot]][game]

## About `==`

The `==` or loose equality operator (and its counterpart `!=`) in JavaScript tries to save the user from having to explicitly convert (cast) values to a common type to make comparisons, so, for example, `"5" == 5` implicitly converts (coerces) the string `"5"` to a number, so the comparison 'just works'. Without loose equality, the same comparison would need to be expressed as either `Number("5") == 5` or `"5" == String(5)`, or, at the shortest, `+"5" == 5` to be true.

The general principle behind having implicit type conversion is called _weak typing_, and it's useful to the degree that it makes code more terse, but the flip side is that the implicit conversion rules are basically guesswork about what the user would expect, and, as such, can guess wrong and lead to unexpected results.

### `==` doesn't check for truthiness or falsiness

Values that convert to either `true` or `false` are called _truthy_ or _falsy_; for example, `0` is falsy because `!!0` or `Boolean(0)` result in `false`. Other examples of falsy values are empty strings, `null` and `undefined`. Meanwhile, all objects (except `document.all`) are truthy, so `!![]` (array object converted to boolean) results in `true`.

One would reasonably expect that being truthy also implies `== true` and falsy implies `== false`, but that's not the case: `[]` is truthy, but `[] == true` is actually false.

### `==` breaks transitivity

Transitivity means that if A equals B and B equals C, then A should equal C, but this is not always true with `==`; for example, `'' == 0`, and `0 == '0'`, but `'' != '0'`.

### `===` isn't a panacea for typing issues

Tripple equals or [strict equality checking rules][strict-rules] are much simpler than `==`; objects are compared by identity and primitives by value (roughly speaking), but it's still possible to create subtle type-related error conditions by forgetting to convert the compared values to the same type. For example, the user might compare `"1" === 2`, intending to compare numbers, and the resulting `false` would suggest that the comparison is working correctly, even though `"2" === 2` would fail.

A language like TypeScript would catch these issues, because static typing follows the _fail-fast_ design principle, while dynamic typing ultimately follows _garbage in, garbage out_ – the responsibility is on the user to make sure that the comparison is sound.

## Trivia

Brendan Eich was asked to add the loose equality checking rules by a coworker in Netscape and considers it a mistake.<sup>[citation needed]</sup>

## Motivation

The initial reason to make this game was to try out state management with [immer-wieder], but it's also to demonstrate that the `==` rules are easy to get wrong even if you feel like you're familiar with them. It's in response to claims like this one by the well-known author [getify][getify]:

> However, implicit coercion is a mechanism that can be learned, and moreover should be learned by anyone wishing to take JavaScript programming seriously. Not only is it not confusing once you learn the rules, it can actually make your programs better! The effort is well worth it.

If the implicit coercion rules were as non-confusing as claimed by getify, most experienced JavaScript users would be able to get close to perfect scores in this game, but there are many reports about giving it a serious attempt and being surprised by the poor results, including from seasoned users.

## Emojis

The game uses emojis; your system and browser should preferably support [color fonts] and have an emoji font like [EmojiOne] or [Noto Color Emoji] installed for the emojis to display properly. If not, the game will provide fallback SVG images from [emojitwo] (using [emoji-extractor]).

## Build

```sh
npm i
npm run build # or: npm run start
```

## Adding a translation

The translation string template is [translations/en-US.json][template], and new translations need to be registered in [translationData.js].

## Tools used

- [immer-wieder]
- [es2015-i18n-tag](https://github.com/skolmer/es2015-i18n-tag)

## License

MIT

## Author

[slikts](https://untu.ms) &lt;dabas@untu.ms>

## Other web-related games

- [Flexbox Froggy](https://flexboxfroggy.com/) – learn CSS [flexbox](https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layout/Flexbox)
- [Grid Garden](https://cssgridgarden.com/) – learn CSS [grid](https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layout/Grids)
- [WarriorJS](https://warriorjs.com/) – control a game character using JS

[table]: https://github.com/dorey/Javascript-Equality-Table/
[wikipedia]: https://en.wikipedia.org/wiki/Strong_and_weak_typing
[reorder]: https://algassert.com/visualization/2014/03/27/Better-JS-Equality-Table.html
[immer-wieder]: https://github.com/drcmda/immer-wieder
[getify]: https://github.com/getify/You-Dont-Know-JS/blob/master/up%20%26%20going/ch1.md#converting-between-types
[visual]: https://i.imgur.com/rWoBHj4.png
[color fonts]: https://www.colorfonts.wtf/
[emojione]: https://www.emojione.com/
[noto color emoji]: https://www.google.com/get/noto/help/emoji/
[screenshot]: https://raw.githubusercontent.com/slikts/js-equality-game/assets/screenshot.png
[game]: https://slikts.github.io/js-equality-game/
[emojitwo]: https://emojitwo.github.io/
[emoji-extractor]: https://github.com/slikts/emoji-extractor
[strict-rules]: https://www.ecma-international.org/ecma-262/9.0/index.html#sec-strict-equality-comparison
[abstract-rules]: https://www.ecma-international.org/ecma-262/9.0/index.html#sec-abstract-equality-comparison
[template]: https://github.com/slikts/js-equality-game/blob/master/src/translations/en-US.json
[translationData.js]: https://github.com/slikts/js-equality-game/blob/master/src/translationData.js

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