Export-ing conventions

Airbnb style guides [10] do not define any specific export style, other than:

10.6 In modules with a single export, prefer default export over named export.

Which one is the preferred style in the following cases (feel free to suggest better ones):

Single export

• Inline export

export default foo = () => { ... }

• Separate export (after definition)

const foo = () => { ... };
export default foo;
const other = () => { ... };

• Separate export (at the end of file)

const foo = () => { ... };
const boo = () => { ... };
export default foo;

Multiple exports

• Inline exports

export foo = () => { ... }
export boo = () => { ... }

• Separate export (after definition)

const foo = () => { ... }
export foo;
const boo = () => { ... }
export boo;

• Separate export (at the end of file)

const foo = () => { ... }
const boo = () => { ... }
export { foo, boo };

• Wrapper export

export const wrapper = {
  foo: () => { ... }
  boo: () => { ... }
}

[alex-mitchem]

Tests should absolutely not only be end to end, its the entire reason smaller functions are considered best practise, because its easier to test a small function than a large function. As for you previous comment, I’m not sure I understand. They don’t have to be exported but can be imported?

[ljharb]

In most cases, you should be exporting one conceptual thing from a module. In other words, if you have both “foo” and “boo”, those are two modules and thus should be export defaulted from two separate files.

If you insist on having them in the same file (there are some use cases where this makes sense, but not many), then you should be using multiple named exports.

When exporting one thing, and inline export is nicer because it ensures that you can not change the binding later (ie, export default function foo() {}; is better than function foo() {} ; export default foo;)

As far as positioning, there will soon be a linter rule in eslint-plugin-import that will require that all export statements are grouped together - so I’d recommend grouping them together and putting them at the bottom of the file.