@stylistic/js/

generator-star-spacing

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.

Here is an example of a generator function:

/*eslint-env es6*/

function* generator() {
    yield "44";
    yield "55";
}

This is also valid:

/*eslint-env es6*/

function *generator() {
    yield "44";
    yield "55";
}

This is valid as well:

/*eslint-env es6*/

function * generator() {
    yield "44";
    yield "55";
}

To keep a sense of consistency when using generators this rule enforces a single position for the *.

Rule Details

This rule aims to enforce spacing around the * of generator functions.

Options

The rule takes one option, an object, which has two keys "before" and "after" having boolean values true or false.

• "before" enforces spacing between the * and the function keyword. If it is true, a space is required, otherwise spaces are disallowed.

  In object literal shorthand methods, spacing before the * is not checked, as they lack a function keyword.

• "after" enforces spacing between the * and the function name (or the opening parenthesis for anonymous generator functions). If it is true, a space is required, otherwise spaces are disallowed.

The default is {"before": true, "after": false}.

An example configuration:

"generator-star-spacing": ["error", {"before": true, "after": false}]

And the option has shorthand as a string keyword:

• {"before": true, "after": false} → "before"
• {"before": false, "after": true} → "after"
• {"before": true, "after": true} → "both"
• {"before": false, "after": false} → "neither"

An example of shorthand configuration:

"generator-star-spacing": ["error", "after"]

Additionally, this rule allows further configurability via overrides per function type.

• named provides overrides for named functions
• anonymous provides overrides for anonymous functions
• method provides overrides for class methods or property function shorthand

An example of a configuration with overrides:

"generator-star-spacing": ["error", {
    "before": false,
    "after": true,
    "anonymous": "neither",
    "method": {"before": true, "after": true}
}]

In the example configuration above, the top level "before" and "after" options define the default behavior of the rule, while the "anonymous" and "method" options override the default behavior. Overrides can be either an object with "before" and "after", or a shorthand string as above.

Examples

before

Examples of correct code for this rule with the "before" option:

/*eslint @stylistic/js/generator-star-spacing: ["error", {"before": true, "after": false}]*/
/*eslint-env es6*/

function *generator() {}

var anonymous = function *() {};

var shorthand = { *generator() {} };

correct

after

Examples of correct code for this rule with the "after" option:

/*eslint @stylistic/js/generator-star-spacing: ["error", {"before": false, "after": true}]*/
/*eslint-env es6*/

function* generator() {}

var anonymous = function* () {};

var shorthand = { * generator() {} };

correct

both

Examples of correct code for this rule with the "both" option:

/*eslint @stylistic/js/generator-star-spacing: ["error", {"before": true, "after": true}]*/
/*eslint-env es6*/

function * generator() {}

var anonymous = function * () {};

var shorthand = { * generator() {} };

correct

neither

Examples of correct code for this rule with the "neither" option:

/*eslint @stylistic/js/generator-star-spacing: ["error", {"before": false, "after": false}]*/
/*eslint-env es6*/

function*generator() {}

var anonymous = function*() {};

var shorthand = { *generator() {} };

correct

Examples of incorrect code for this rule with overrides present:

/*eslint @stylistic/js/generator-star-spacing: ["error", {
    "before": false,
    "after": true,
    "anonymous": "neither",
    "method": {"before": true, "after": true}
}]*/
/*eslint-env es6*/

function 
*
 generator() {}

var anonymous = function
*
 () {};

var shorthand = { 
*
generator() {} };

class Class { static
*
 method() {} }

incorrect

Examples of correct code for this rule with overrides present:

/*eslint @stylistic/js/generator-star-spacing: ["error", {
    "before": false,
    "after": true,
    "anonymous": "neither",
    "method": {"before": true, "after": true}
}]*/
/*eslint-env es6*/

function* generator() {}

var anonymous = function*() {};

var shorthand = { * generator() {} };

class Class { static * method() {} }

correct

When Not To Use It

If your project will not be using generators or you are not concerned with spacing consistency, you do not need this rule.