orionsoft-react-scripts
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Orionsoft Configuration and scripts for Create React App.
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# JavaScript Standard Style
[](https://github.com/feross/standard)
This is a TL;DR of the [standard](https://github.com/feross/standard) JavaScript
rules.
The best way to learn about `standard` is to just install it and give it a try on
your code.
## Rules
* **Use 2 spaces** for indentation.
```js
function hello (name) {
console.log('hi', name)
}
```
* **Use single quotes for strings** except to avoid escaping.
```js
console.log('hello there')
$("<div class='box'>")
```
* **No unused variables.**
```js
function myFunction () {
var result = something() // ✗ avoid
}
```
* **Add a space after keywords.**
```js
if (condition) { ... } // ✓ ok
if(condition) { ... } // ✗ avoid
```
* **Add a space before a function declaration's parentheses.**
```js
function name (arg) { ... } // ✓ ok
function name(arg) { ... } // ✗ avoid
run(function () { ... }) // ✓ ok
run(function() { ... }) // ✗ avoid
```
* **Always use** `===` instead of `==`.<br>
Exception: `obj == null` is allowed to check for `null || undefined`.
```js
if (name === 'John') // ✓ ok
if (name == 'John') // ✗ avoid
```
```js
if (name !== 'John') // ✓ ok
if (name != 'John') // ✗ avoid
```
* **Infix operators** must be spaced.
```js
// ✓ ok
var x = 2
var message = 'hello, ' + name + '!'
```
```js
// ✗ avoid
var x=2
var message = 'hello, '+name+'!'
```
* **Commas should have a space** after them.
```js
// ✓ ok
var list = [1, 2, 3, 4]
function greet (name, options) { ... }
```
```js
// ✗ avoid
var list = [1,2,3,4]
function greet (name,options) { ... }
```
* **Keep else statements** on the same line as their curly braces.
```js
// ✓ ok
if (condition) {
// ...
} else {
// ...
}
```
```js
// ✗ avoid
if (condition) {
// ...
}
else {
// ...
}
```
* **For multi-line if statements,** use curly braces.
```js
// ✓ ok
if (options.quiet !== true) console.log('done')
```
```js
// ✓ ok
if (options.quiet !== true) {
console.log('done')
}
```
```js
// ✗ avoid
if (options.quiet !== true)
console.log('done')
```
* **Always handle the** `err` function parameter.
```js
// ✓ ok
run(function (err) {
if (err) throw err
window.alert('done')
})
```
```js
// ✗ avoid
run(function (err) {
window.alert('done')
})
```
* **Always prefix browser globals** with `window.`.<br>
Exceptions are: `document`, `console` and `navigator`.
```js
window.alert('hi') // ✓ ok
```
* **Multiple blank lines not allowed.**
```js
// ✓ ok
var value = 'hello world'
console.log(value)
```
```js
// ✗ avoid
var value = 'hello world'
console.log(value)
```
* **For the ternary operator** in a multi-line setting, place `?` and `:` on their own lines.
```js
// ✓ ok
var location = env.development ? 'localhost' : 'www.api.com'
// ✓ ok
var location = env.development
? 'localhost'
: 'www.api.com'
// ✗ avoid
var location = env.development ?
'localhost' :
'www.api.com'
```
* **For var declarations,** write each declaration in its own statement.
```js
// ✓ ok
var silent = true
var verbose = true
// ✗ avoid
var silent = true, verbose = true
// ✗ avoid
var silent = true,
verbose = true
```
* **Wrap conditional assignments** with additional parentheses. This makes it clear that the expression is intentionally an assignment (`=`) rather than a typo for equality (`===`).
```js
// ✓ ok
while ((m = text.match(expr))) {
// ...
}
// ✗ avoid
while (m = text.match(expr)) {
// ...
}
```
*
## Semicolons
* No semicolons. (see: [1](http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding), [2](http://inimino.org/%7Einimino/blog/javascript_semicolons), [3](https://www.youtube.com/watch?v=gsfbh17Ax9I))
```js
window.alert('hi') // ✓ ok
window.alert('hi'); // ✗ avoid
```
* Never start a line with `(`, `[`, or `` ` ``. This is the only gotcha with omitting semicolons, and standard protects you from this potential issue.
```js
// ✓ ok
;(function () {
window.alert('ok')
}())
// ✗ avoid
(function () {
window.alert('ok')
}())
```
```js
// ✓ ok
;[1, 2, 3].forEach(bar)
// ✗ avoid
[1, 2, 3].forEach(bar)
```
```js
// ✓ ok
;`hello`.indexOf('o')
// ✗ avoid
`hello`.indexOf('o')
```
Note: If you're often writing code like this, you may be trying to be too clever.
Clever short-hands are discouraged, in favor of clear and readable expressions, whenever
possible.
Instead of this:
```js
;[1, 2, 3].forEach(bar)
```
This is much preferred:
```js
var nums = [1, 2, 3]
nums.forEach(bar)
```
## Helpful reading
- [An Open Letter to JavaScript Leaders Regarding Semicolons][1]
- [JavaScript Semicolon Insertion – Everything you need to know][2]
##### And a helpful video:
- [Are Semicolons Necessary in JavaScript? - YouTube][3]
All popular code minifiers in use today use AST-based minification, so they can
handle semicolon-less JavaScript with no issues (since semicolons are not required
in JavaScript).
##### Excerpt from *["An Open Letter to JavaScript Leaders Regarding Semicolons"][1]*:
[Relying on automatic semicolon insertion] is quite safe, and perfectly valid JS that every browser understands. Closure compiler, yuicompressor, packer, and jsmin all can properly minify it. There is no performance impact anywhere.
I am sorry that, instead of educating you, the leaders in this language community have given you lies and fear. That was shameful. I recommend learning how statements in JS are actually terminated (and in which cases they are not terminated), so that you can write code that you find beautiful.
In general, `\n` ends a statement unless:
1. The statement has an unclosed paren, array literal, or object literal or ends in some
other way that is not a valid way to end a statement. (For instance, ending with `.`
or `,`.)
2. The line is `--` or `++` (in which case it will decrement/increment the next token.)
3. It is a `for()`, `while()`, `do`, `if()`, or `else`, and there is no `{`
4. The next line starts with `[`, `(`, `+`, `*`, `/`, `-`, `,`, `.`, or some other
binary operator that can only be found between two tokens in a single expression.
The first is pretty obvious. Even JSLint is ok with `\n` chars in JSON and parenthesized constructs, and with `var` statements that span multiple lines ending in `,`.
The second is super weird. I’ve never seen a case (outside of these sorts of conversations) where you’d want to do write `i\n++\nj`, but, point of fact, that’s parsed as `i; ++j`, not `i++; j`.
The third is well understood, if generally despised. `if (x)\ny()` is equivalent to `if (x) { y() }`. The construct doesn’t end until it reaches either a block, or a statement.
`;` is a valid JavaScript statement, so `if(x);` is equivalent to `if(x){}` or, “If x, do nothing.” This is more commonly applied to loops where the loop check also is the update function. Unusual, but not unheard of.
The fourth is generally the fud-inducing “oh noes, you need semicolons!” case. But, as it turns out, it’s quite easy to *prefix* those lines with semicolons if you don’t mean them to be continuations of the previous line. For example, instead of this:
```js
foo();
[1,2,3].forEach(bar);
```
you could do this:
```js
foo()
;[1,2,3].forEach(bar)
```
The advantage is that the prefixes are easier to notice, once you are accustomed to never seeing lines starting with `(` or `[` without semis.
*End quote from "An Open Letter to JavaScript Leaders Regarding Semicolons".*
[1]: http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding
[2]: http://inimino.org/~inimino/blog/javascript_semicolons
[3]: https://www.youtube.com/watch?v=gsfbh17Ax9I