import/prefer-default-export

If a file exports one thing, that thing is what the file is for, and a default export says so. Anyone who imports it doesn't have to look up the name.

The rule skips a file if it has a default export, an export *, or an exported type or interface.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"import/prefer-default-export" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"import/prefer-default-export" = ["error", {
  target = "single", # "single" or "any"
}]

Examples#

example.js1 problem

export function formatDate(date) {
  return date.toISOString();
}

example.jsNo problems

export default function formatDate(date) {
  return date.toISOString();
}

example.jsNo problems

export function formatDate(date) {}
export function formatTime(date) {}

example.tsNo problems

export type UserId = number;

Options#

Option	Default	What it does
`target`	`"single"`	`"single"` reports a file with exactly one named export. `"any"` reports every file that has named exports and no default export.

With "any", this is reported:

example.jswith { "target": "any" }1 problem

export function formatDate(date) {}
export function formatTime(date) {}

When not to use it#

Named exports keep the same name everywhere, which helps auto-import and renaming. If your project prefers them, use import/no-default-export and leave this rule off.