ES 模块仅支持几种语法变体,以便进行静态分析。
根据参考 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/export#Syntax,变化是:
export { name1, name2, …, nameN };
export { variable1 as name1, variable2 as name2, …, nameN };
export let name1, name2, …, nameN; // also var, function
export let name1 = …, name2 = …, …, nameN; // also var, const
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 foo
不在其中。它不受支持且无法使用。