es6 export 的 function 不能指定参数传参吗?

//file.js
export const f = function (a,b) {
    console.log(a)
    console.log(b)
}
//main.js
import * as foo from "file.js"
foo.f(b=1);

Uncaught ReferenceError: b is not defined
//报错在 foo.f(b=1)这行.

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应该是在函数声明的时候，赋默认值吧？

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foo.f({b:1});

ref: http://es6.ruanyifeng.com/#docs/function