CommonJS vs ES Modules

// ES Modules
export default function() {}
export const named = {};

// CommonJS
module.exports = function() {}
module.exports.named = {};

CommonJS doesn't support default exports
ES Modules can only have one default export, CommonJS can have multiple
ES Modules handle default exports as distinct from named exports, CommonJS doesn't distinguish them
Default exports are handled differently in each system: 1) ES Modules have a distinct syntax for default exports (export default) separate from named exports, 2) In CommonJS, the default export is just the value assigned to module.exports, with named exports as properties, 3) ES Modules enforce that there can only be one default export per module, 4) CommonJS doesn't have a true concept of default export vs named exports - it's all just properties of the exports object, 5) ES Modules' approach provides clearer intent and better tooling support, 6) CommonJS's approach is more flexible but less explicit, 7) This difference affects how modules are consumed and how bundlers process the code.
Default exports are slower in CommonJS