babel-plugin-transform-export-default-name

babel-plugin-transform-export-default-name

Babel plugin that transforms export default of anonymous functions to named function export.

Plugin uses the name of the target file to create a temporary variable. Target resource (arrow function or an anonymous function) is assigned to the latter temporary variable. Temporary value is used in place of function in the export declaration.

Implementation

Values that are affected:

• anonymous function
• arrow function
• anonymous class

Named function, named class and other object as well as literal values are not transformed.

Export Name

The name used for a temporary variable is derived from the name of the file (excluding .js extension). _.camelCase is used to sanitize file name (i.e. foo-bar.js becomes fooBar).

Problem

Executing a function without a name (arrow function or an anonymous function) appears as an (anonymous function) in the stack trace, e.g.

(() => {
    throw new Error('Hello, World!');
})();

However, if an arrow function is defined on the right-hand-side of an assignment expression, the engine will take the name on the left-hand-side and use it to set the arrow function's .name, e.g.

let test;

test = () => {
    throw new Error('Hello, World!');
};

test();

When you export an anonymous function using export default, this function will appear as an (anonymous function) the stack trace. babel-plugin-transform-export-default-name plugin transforms the code to assign function a name before it is exported.

./index.js

import foo from './foo';

foo();

./foo.js

import bar from './bar';

export default () => {
    bar();
};

./bar.js

import baz from './baz';

export default () => {
    baz();
};

./baz.js

export default () => {
    throw new Error('test');
};

Example

Input file is ./foo.js.

Input code:

export default () => {};

Output code:

let foo = () => {};

export default foo;

Usage

Add to .babelrc:

{
    "plugins": [
        "transform-export-default-name"
    ]
}