In exporting files, this rule checks if there is default export or not.
javascript
"import/prefer-default-export": [
( "off" | "warn" | "error" ),
{ "target": "single" | "any" } // default is "single"
]
There are two options available: single and any. By default, if you do not specify the option, rule will assume it is single.
Definition: When there is only a single export from a module, prefer using default export over named export.
How to setup config file for this rule:
```javascript // you can manually specify it "rules": { "import/prefer-default-export": [ ( "off" | "warn" | "error" ), { "target": "single" } ] }
// config setup below will also work "rules": { "import/prefer-default-export": "off" | "warn" | "error" } ```
The following patterns are considered warnings:
```javascript // bad.js
// There is only a single module export and it's a named export. export const foo = 'foo';
```
The following patterns are not warnings:
```javascript // good1.js
// There is a default export. export const foo = 'foo'; const bar = 'bar'; export default bar; ```
```javascript // good2.js
// There is more than one named export in the module. export const foo = 'foo'; export const bar = 'bar'; ```
```javascript // good3.js
// There is more than one named export in the module const foo = 'foo'; const bar = 'bar'; export { foo, bar } ```
```javascript // good4.js
// There is a default export. const foo = 'foo'; export { foo as default } ```
```javascript // export-star.js
// Any batch export will disable this rule. The remote module is not inspected. export * from './other-module' ```
Definition: any exporting file must contain a default export.
How to setup config file for this rule:
javascript
// you have to manually specify it
"rules": {
"import/prefer-default-export": [
( "off" | "warn" | "error" ),
{ "target": "any" }
]
}
The following patterns are not considered warnings:
```javascript // good1.js
//has default export export default function bar() {}; ```
```javascript // good2.js
// has default export let foo; export { foo as default } ```
```javascript // good3.js
//contains multiple exports AND default export export const a = 5; export function bar(){}; let foo; export { foo as default } ```
```javascript // good4.js
// does not contain any exports => file is not checked by the rule import * as foo from './foo'; ```
```javascript // export-star.js
// Any batch export will disable this rule. The remote module is not inspected. export * from './other-module' ```
The following patterns are considered warnings:
```javascript // bad1.js
//has 2 named exports, but no default export export const foo = 'foo'; export const bar = 'bar'; ```
```javascript // bad2.js
// does not have default export let foo, bar; export { foo, bar } ```
```javascript // bad3.js
// does not have default export export { a, b } from "foo.js" ```
```javascript // bad4.js
// does not have default export let item; export const foo = item; export { item }; ```