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Merge pull request #783 from nyuszika7h/patch-3
RULES.md: Add more examples; minor fixes
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‎RULES.md

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@@ -570,6 +570,7 @@ your code.
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```js
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eval( "var result = user." + propName ) // ✗ avoid
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var result = user[propName] // ✓ ok
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```
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* **No reassigning exceptions in `catch` clauses.**
@@ -656,6 +657,14 @@ your code.
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case 2:
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doSomethingElse()
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}
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switch (filter) {
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case 1:
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doSomething()
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// fallthrough // ✓ ok
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case 2:
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doSomethingElse()
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}
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```
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* **No floating decimals.**
@@ -689,7 +698,8 @@ your code.
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eslint: [`no-implied-eval`](http://eslint.org/docs/rules/no-implied-eval)
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```js
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setTimeout("alert('Hello world')") // ✗ avoid
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setTimeout("alert('Hello world')") // ✗ avoid
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setTimeout(function () { alert('Hello world') }) // ✓ ok
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```
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* **No function declarations in nested blocks.**
@@ -716,7 +726,7 @@ your code.
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eslint: [`no-irregular-whitespace`](http://eslint.org/docs/rules/no-irregular-whitespace)
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```js
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function myFunc() /*<NBSP>*/{} // ✗ avoid
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function myFunc () /*<NBSP>*/{} // ✗ avoid
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```
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* **No using `__iterator__`.**
@@ -761,7 +771,7 @@ your code.
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}
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function myFunc () {
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myOtherFunc() // ✓ ok
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myOtherFunc() // ✓ ok
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}
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```
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@@ -897,6 +907,8 @@ your code.
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```js
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const regexp = /test value/ // ✗ avoid
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const regexp = /test {3}value/ // ✓ ok
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const regexp = /test value/ // ✓ ok
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```
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@@ -1128,6 +1140,7 @@ your code.
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}
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const user = { name: 'Jane Doe', age: 30, username: 'jdoe86' } // ✓ ok
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const user = {
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name: 'Jane Doe',
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age: 30,
@@ -1160,7 +1173,7 @@ your code.
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fn(...args) // ✓ ok
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```
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* **Semicolon's must have a space after and no space before.**
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* **Semicolons must have a space after and no space before.**
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eslint: [`semi-spacing`](http://eslint.org/docs/rules/semi-spacing)
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@@ -1178,7 +1191,7 @@ your code.
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if (admin) {...} // ✓ ok
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```
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* **No spaces inside parens.**
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* **No spaces inside parentheses.**
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eslint: [`space-in-parens`](http://eslint.org/docs/rules/space-in-parens)
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@@ -1193,7 +1206,7 @@ your code.
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```js
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typeof!admin // ✗ avoid
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typof !admin // ✓ ok
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typeof !admin // ✓ ok
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```
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* **Use spaces inside comments.**
@@ -1203,6 +1216,9 @@ your code.
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```js
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//comment // ✗ avoid
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// comment // ✓ ok
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/*comment*/ // ✗ avoid
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/* comment */ // ✓ ok
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```
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* **No spacing in template strings.**
@@ -1223,7 +1239,7 @@ your code.
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if (isNaN(price)) { } // ✓ ok
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```
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* **`typeof` must be compared to valid string.**
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* **`typeof` must be compared to a valid string.**
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eslint: [`valid-typeof`](http://eslint.org/docs/rules/valid-typeof)
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@@ -1232,14 +1248,15 @@ your code.
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typeof name === 'undefined' // ✓ ok
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```
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* **Immediately Invoked Function Expressions (IFFE's) must be wrapped.**
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* **Immediately Invoked Function Expressions (IIFEs) must be wrapped.**
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eslint: [`wrap-iife`](http://eslint.org/docs/rules/wrap-iife)
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```js
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const getName = function () { }() // ✗ avoid
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const getName = (function () { }) // ✓ ok
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const getName = (function () { }()) // ✓ ok
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const getName = (function () { })() // ✓ ok
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```
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* **The `*` in `yield*`expressions must have a space before and after.**
@@ -1314,7 +1331,7 @@ your code.
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;[1, 2, 3].forEach(bar)
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```
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This is much preferred:
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This is strongly preferred:
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```js
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var nums = [1, 2, 3]
@@ -1337,44 +1354,42 @@ in JavaScript).
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##### Excerpt from *["An Open Letter to JavaScript Leaders Regarding Semicolons"][1]*:
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[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.
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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.
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In general, `\n` ends a statement unless:
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1. The statement has an unclosed paren, array literal, or object literal or ends in some
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other way that is not a valid way to end a statement. (For instance, ending with `.`
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or `,`.)
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2. The line is `--` or `++` (in which case it will decrement/increment the next token.)
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3. It is a `for()`, `while()`, `do`, `if()`, or `else`, and there is no `{`
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4. The next line starts with `[`, `(`, `+`, `*`, `/`, `-`, `,`, `.`, or some other
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binary operator that can only be found between two tokens in a single expression.
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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 `,`.
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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`.
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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.
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`;` 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.
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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:
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```js
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foo();
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[1,2,3].forEach(bar);
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```
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you could do this:
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```js
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foo()
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;[1,2,3].forEach(bar)
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```
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The advantage is that the prefixes are easier to notice, once you are accustomed to never seeing lines starting with `(` or `[` without semis.
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*End quote from "An Open Letter to JavaScript Leaders Regarding Semicolons".*
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> [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.
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>
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> 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.
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>
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> In general, `\n` ends a statement unless:
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> 1. The statement has an unclosed paren, array literal, or object literal or ends in some
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> other way that is not a valid way to end a statement. (For instance, ending with `.`
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> or `,`.)
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> 2. The line is `--` or `++` (in which case it will decrement/increment the next token.)
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> 3. It is a `for()`, `while()`, `do`, `if()`, or `else`, and there is no `{`
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> 4. The next line starts with `[`, `(`, `+`, `*`, `/`, `-`, `,`, `.`, or some other
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> binary operator that can only be found between two tokens in a single expression.
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>
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> 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 `,`.
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>
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> 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`.
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>
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> 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.
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>
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> `;` 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.
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>
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> 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:
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>
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> ```js
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> foo();
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> [1,2,3].forEach(bar);
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> ```
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>
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> you could do this:
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>
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> ```js
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> foo()
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> ;[1,2,3].forEach(bar)
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> ```
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>
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> The advantage is that the prefixes are easier to notice, once you are accustomed to never seeing lines starting with `(` or `[` without semis.
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[1]: http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding
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[2]: http://inimino.org/~inimino/blog/javascript_semicolons

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