When writing modern JavaScript, especially in collaborative environments, maintaining consistent coding practices is essential. ESLint, a popular linting tool, helps enforce rules to keep code readable and maintainable. One of its stylistic preferences is the use of default exports over named exports in modules. The ESLint ruleimport/prefer-default-exportencourages this practice. While seemingly minor, this choice can have a significant impact on how code is structured and shared across a project. Understanding the reasons behind the prefer default export rule can help developers write more effective and consistent JavaScript code.
Understanding Exports in JavaScript
Default vs. Named Exports
JavaScript modules can export values using either default exports or named exports. A default export allows a single value or object to be exported from a module, while named exports allow multiple values to be exported by name.
- Default Export:
export default MyComponent; - Named Export:
export { MyComponent };
When importing a default export, the developer can choose any name for the import:
import MyComponent from './MyComponent';For named exports, the import must match the exported name exactly:
import { MyComponent } from './MyComponent';The ESLint Rule: import/prefer-default-export
What It Does
Theimport/prefer-default-exportrule in ESLint recommends using a default export when there is only a single export from a module. This makes it easier to import without worrying about the exported name, which can reduce confusion and typing errors.
This rule is part of theeslint-plugin-importset of rules, which focuses on managing ES6 module syntax and improving import/export consistency. The idea is that if a module only has one export, a default export provides a simpler and cleaner syntax.
How to Enable the Rule
To use this rule, ESLint must be configured with the plugin. A typical ESLint configuration to enable this rule looks like:
{ 'plugins': ['import'], 'rules': { 'import/prefer-default-export': 'warn' } }Why Prefer Default Export?
Cleaner Import Syntax
Default exports allow more flexibility in naming when importing. This can be helpful when trying to keep code short and readable. For example, when importing a React component:
import Button from './Button';This reads more naturally and does not require curly braces or remembering the exact export name.
Better Developer Experience
In a codebase where modules mostly export a single component or utility function, using default export allows consistent import style and avoids repetition. Developers don’t have to wonder whether to import using curly braces or not they can rely on a standard approach.
Compatibility With Tools
Some bundlers, transpilers, or frameworks expect or handle default exports more cleanly. While ES modules are supported broadly now, legacy tools or certain frameworks might behave better when default exports are used.
Simplifies Refactoring
When renaming a default export, the file contents do not have to change. You can update the import name without editing the module itself, making it easier to refactor without breaking existing imports.
When Not to Use Default Exports
Multiple Exports in One File
If a module contains more than one export, then named exports are a better option. This allows developers to selectively import only what is needed:
export const add = (a, b) =>a + b; export const subtract = (a, b) =>a - b;Then imported like:
import { add } from './math';Static Analysis Benefits
Named exports improve static analysis tools’ ability to detect unused code. If you import a named export and never use it, linters or bundlers can flag or tree-shake it. With default exports, this analysis can be less precise.
Better API Contracts
Named exports act as a clear contract between the module and its consumers. When multiple exports are expected or when consistency in naming is important, named exports are often preferred for clarity.
Team Preferences and Code Consistency
Enforcing Team Style
While ESLint can enforce the use of default exports, teams may have different preferences based on their coding guidelines. Some teams choose to always use named exports for predictability, while others prefer default exports for their simplicity in single-export modules. The important thing is consistency.
Disabling the Rule
If a team decides that named exports are preferred even for single-export modules, this rule can be disabled in the ESLint config:
{ 'rules': { 'import/prefer-default-export': 'off' } }This allows greater flexibility in coding style, especially in projects where named exports are considered more explicit and easier to manage.
Practical Examples
Default Export Example
// utils/date.js export default function formatDate(date) { return date.toLocaleDateString(); }// usage import formatDate from './utils/date';Named Export Alternative
// utils/date.js export function formatDate(date) { return date.toLocaleDateString(); }// usage import { formatDate } from './utils/date';Both approaches are valid, but ESLint’simport/prefer-default-exportwill suggest the first format ifformatDateis the only function in the file.
Balancing Preference with Practicality
Context Matters
Whether or not to use default exports depends heavily on project needs. The ESLint ruleimport/prefer-default-exportencourages a cleaner, simpler syntax when it makes sense. However, it should not override logical or organizational clarity.
Working in Large Codebases
In large applications, modules often contain multiple functions, components, or constants. In these cases, named exports offer better scalability and clarity. It is worth evaluating this rule in the context of how the team organizes code.
The ESLint ruleimport/prefer-default-exportencourages the use of default exports when a module only contains a single export. It promotes simpler import statements and consistent code style. While there are good arguments for and against default exports, the key lies in using the right tool for the right job. Default exports work best in small, focused modules. Named exports, on the other hand, shine in more complex scenarios. By understanding both approaches and how ESLint can guide style, developers can maintain clean, readable, and maintainable JavaScript code across projects.