Enforces consistent spacing around the asterisk in generator functions.

Generators are a new type of function in ECMAScript 6 that can return multiple values over time.

These special functions are indicated by placing an `*` after the `function` keyword.

Requires or disallows strict mode directives in the global scope.

Strict mode is enabled by using the following pragma in your code:

Disallows arrow functions where test conditions are expected.

Arrow functions (`=>`) are similar in syntax to some comparison operators (`>`, `<`, `<=`, and `>=`). This rule warns against using the arrow function syntax in places where a condition is expected. Even if the arguments of the arrow function are wrapped with parens, this rule still warns about it.

Disallows trailing commas in object and array literals.

Trailing commas in object literals are valid according to the ECMAScript 5 (and ECMAScript 3!) spec, however IE8 (when not in IE8 document mode) and below will throw an error when it encounters trailing commas in JavaScript.

Disallows empty character classes in regular expressions.

Empty character classes in regular expressions do not match anything and can result in code that may not work as intended.

Disallows labels for anything other than loops and switches.

Labeled statements are only used in conjunction with labeled break and continue statements. ECMAScript has no goto statement.

Disallows strict mode directives when already in strict mode.

The `"use strict";` directive applies to the scope in which it appears and all inner scopes contained within that scope. Therefore, using the `"use strict";` directive in one of these inner scopes is unnecessary.

Disallows unquoted reserved words as property names in object literals.

ECMAScript 3 described as series of keywords and reserved words, such as `if` and `public`, that are used or intended to be used for a core language feature. The specification also indicated that these keywords and reserved words could not be used as object property names without being enclosed in strings. An error occurs in an ECMAScript 3 environment when you use a keyword or reserved word in an object literal. For example:

Disallows spaces before semicolons.

JavaScript allows for placing unnecessary spaces between an expression and the closing semicolon.

Disallows unnecessary parentheses around function expressions.

Although it's possible to wrap functions in parentheses, this can be confusing when the code also contains immediately-invoked function expressions (IIFEs) since parentheses are often used to make this distinction. For example: