eslint/func-style Style

🚧 An auto-fix is still under development.

What it does

Enforce the consistent use of either function declarations or expressions assigned to variables

Why is this bad?

This rule enforces a particular type of function style, either function declarations or expressions assigned to variables. You can specify which you prefer in the configuration.

Examples

// function declaration function doSomething() { // ... }

// arrow function expression assigned to a variable const doSomethingElse = () => { // ... };

// function expression assigned to a variable const doSomethingAgain = function() { // ... };

Examples of incorrect code for this rule with the default "expression" option:

/*eslint func-style: ["error", "expression"]*/

function foo() {
  // ...
}

Examples of incorrect code for this rule with the "declaration" option:

/*eslint func-style: ["error", "declaration"]*/
var foo = function () {
  // ...
};

var foo = () => {};

Examples of incorrect code for this rule with the "declaration" and {"overrides": { "namedExports": "expression" }} option:

/*eslint func-style: ["error", "declaration", { "overrides": { "namedExports": "expression" } }]*/
export function foo() {
  // ...
}

Examples of incorrect code for this rule with the "expression" and {"overrides": { "namedExports": "declaration" }} option:

/*eslint func-style: ["error", "expression", { "overrides": { "namedExports": "declaration" } }]*/
export var foo = function () {
  // ...
};

export var bar = () => {};

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

/*eslint func-style: ["error", "expression"]*/
var foo = function() {
    // ...
};

Examples of correct code for this rule with the "declaration" option:
```js
/*eslint func-style: ["error", "declaration"]*/
function foo() {
    // ...
}
 // Methods (functions assigned to objects) are not checked by this rule
SomeObject.foo = function() {
    // ...
};

Examples of additional correct code for this rule with the "declaration", { "allowArrowFunctions": true } options:

/*eslint func-style: ["error", "declaration", { "allowArrowFunctions": true }]*/
var foo = () => {};

Examples of correct code for this rule with the "declaration" and {"overrides": { "namedExports": "expression" }} option:

/*eslint func-style: ["error", "declaration", { "overrides": { "namedExports": "expression" } }]*/
export var foo = function () {
  // ...
};
export var bar = () => {};

Examples of correct code for this rule with the "expression" and {"overrides": { "namedExports": "declaration" }} option:

/*eslint func-style: ["error", "expression", { "overrides": { "namedExports": "declaration" } }]*/
export function foo() {
  // ...
}

Examples of correct code for this rule with the {"overrides": { "namedExports": "ignore" }} option:

/*eslint func-style: ["error", "expression", { "overrides": { "namedExports": "ignore" } }]*/
export var foo = function () {
  // ...
};

export var bar = () => {};
export function baz() {
  // ...
}

How to use

To enable this rule in the CLI or using the config file, you can use:

CLI

oxlint --deny func-style

Config (.oxlintrc.json)

{
  "rules": {
    "func-style": "error"
  }
}

References

• Rule Source