@a-la/export

@a-la/export

@a-la/export is a a set of rules for alamode to transpile ESM modules' export statements into CJS modules' module.exports statements in Node.js.

yarn add -E @a-la/export

Table Of Contents

• Table Of Contents
• API
• Output Example
  • Unnamed Default
  • Export From
• Limitations
• Checklist
• Positions Preservation
• Copyright

API

The ÀLaImport is the default export and an array containing a sequence of rules for Replaceable.

import ÀLaExport from '@a-la/import'

Output Example

The set of rules changes export to module.exports statements. module.exports will be bound to the default export if it is present, and all named exports will be assigned to module.exports after that.

Input	Output
/** * Example 1. */ export const example1 = async () => { console.log('named export 1') } /** * Example 2. */ export function example2() { console.log('named export 2') } /** * Example 3. */ function example3() { console.log('named export 3') } /** * Example 4. */ const example4 = async () => { console.log('named export 4') } export { example3, example4 as alias4 } /** * Default Class Example. */ export default class Example { /** * A constructor for the example. * @constructor */ constructor() { console.log('default export') } }	/** * Example 1. */ const example1 = async () => { console.log('named export 1') } /** * Example 2. */ function example2() { console.log('named export 2') } /** * Example 3. */ function example3() { console.log('named export 3') } /** * Example 4. */ const example4 = async () => { console.log('named export 4') } /** * Default Class Example. */ class Example { /** * A constructor for the example. * @constructor */ constructor() { console.log('default export') } } module.exports = Example module.exports.example1 = example1 module.exports.example2 = example2 module.exports.example3 = example3 module.exports.alias4 = example4

Unnamed Default

When there's an unnamed default such as export default class {} or export default async function () {}, it will be replaced in place. Since all named exports will be assigned at the end anyway, there shouldn't be a problem.

Input	Output
export function example1() {} export default class { /** * An unnamed default class. */ constructor() {} } export function example2() {}	function example1() {} module.exports=class { /** * An unnamed default class. */ constructor() {} } function example2() {} module.exports.example1 = example1 module.exports.example2 = example2

Export From

When exporting from another module, some private internal variables are created. It is currently not possible to export a default either as named, or as default from more than one module.

Input	Output
export const example = () => {} export { default, example2, example3 as alias3, } from 'test'	const example = () => {} const $test = require('test'); module.exports = $test module.exports.example = example module.exports.example2 = $test.example2 module.exports.alias3 = $test.example3

Input	Output
export const example = () => {} export { default as example2, } from 'test'	const example = () => {} const $test = require('test'); module.exports.example = example module.exports.example2 = $test

Limitations

• If the default export is a primitive type such as boolean or number, it is not possible to use named exports as well, because module.exports will be binded to the primitive, and further assignments to module.exports.namedExport will not have any effect.

  module.exports = 'STRING' // primitive (string)
  module.exports.example = function () {}
  console.log(module.exports.example) // undefined
  

• Serial exports of declarations are not possible as it's difficult to parse them using a regular expression.

  // not possible
  export const
    a = 'test',
    b = () => {}
  

• When using the export from statement, a private variable for the targeted module will be created, e.g., export { default } from test will create const $test = require('test') variable, therefore a collision could happen if a variable with such name was declared in the code.

Checklist

• export { name1, name2, …, nameN };

• export { variable1 as name1, variable2 as name2, …, nameN };

• export let name1, name2, …, nameN; // also var, const

• export let name1 = …, name2 = …, …, nameN; // also var, const

• export function FunctionName(){...}

• export class ClassName {...}

• export default expression;

• export default function (…) { … } // also class, function*

• export default function name1(…) { … } // also class, function*

• export { name1 as default, … };

• export * from …;

• export { name1, name2, …, nameN } from …;

• export { import1 as name1, import2 as name2, …, nameN } from …;

• export { default } from …;

Positions Preservation

The transform will attempt to preserve line and column numbers as they are for easier generation of source maps by alamode. In future, this might change.

Copyright

(c) À La Mode 2018