Default Exports in TypeScript

Default exports are a powerful feature in TypeScript that allow you to export a single value, function, or class as the main export of a module. They simplify module imports and provide a convenient way to organize your code.

Understanding Default Exports

In TypeScript, you can use the export default keyword to specify a default export for a module. This feature is particularly useful when a module has a primary purpose or a main component that should be easily accessible.

Syntax and Usage

To create a default export, simply add the export default keywords before the value, function, or class you want to export:

// myModule.ts
export default function greet(name: string) {
    return `Hello, ${name}!`;
}

When importing a default export, you can use any name you prefer without curly braces:

// main.ts
import sayHello from './myModule';

console.log(sayHello('Alice')); // Output: Hello, Alice!

Benefits of Default Exports

• Simplified imports: No need to remember specific names when importing.
• Flexibility: You can rename the import without changing the original module.
• Clear module structure: Ideal for modules with a single, primary export.

Default Exports vs Named Exports

While default exports are convenient, TypeScript also supports named exports. The choice between them depends on your module's structure and purpose:

Default Exports	Named Exports
One per module	Multiple per module
Imported without curly braces	Imported with curly braces
Can be renamed during import	Must use exact names (or aliases)

Best Practices

1. Use default exports for modules with a clear, single responsibility.
2. Combine default and named exports when appropriate.
3. Be consistent with your export style across your project.
4. Consider using named exports for utility functions or constants.

Example: Class as Default Export

Default exports are not limited to functions. You can also export classes:

// user.ts
export default class User {
    constructor(public name: string, public age: number) {}

    greet() {
        return `Hello, I'm ${this.name} and I'm ${this.age} years old.`;
    }
}

// main.ts
import UserClass from './user';

const user = new UserClass('Bob', 30);
console.log(user.greet()); // Output: Hello, I'm Bob and I'm 30 years old.

Considerations

While default exports offer simplicity, they can sometimes lead to naming inconsistencies across a large project. It's essential to balance the convenience of default exports with the clarity and predictability of named exports.

For more complex module structures, you might want to explore Export and Import patterns in TypeScript to effectively organize your code.

Conclusion

Default exports in TypeScript provide a straightforward way to export and import primary module functionality. By understanding when and how to use them, you can create more maintainable and intuitive module interfaces in your TypeScript projects.

To dive deeper into TypeScript modules, consider exploring Module Basics and Re-exports for more advanced module management techniques.