I have read docs from MDN, ok, mainly it's good about the new module feature, what makes me confused is the small things about export
, now, let's see:
when I
export function foo(x) {
return x * x;
}
or
export const foo = (x) => {
return x * x
}
both works;
but if
const foo = (x) => {
return x * x
}
export foo // failed
I know here should be export {foo}
, but, why? what's the difference, that should be work. glad to hear some genies ideas.
ES modules support only several syntax variations in order to be statically analyzed.
According to the reference , the variations are:
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
is not among them. It is not supported and cannot be used.
I know here should be
export {foo}
, but why?
Because that's the syntax that was decided for. Notice that it's actually possible to export multiple variables from a single export declaration:
export { foo as foo, bar as bar }
It just doesn't flow well without braces.
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