可选链接 - Function.prototype.apply 被调用未定义，这是未定义的而不是函数

Question

Using optional chaining with function calls causes the expression to automatically return undefined instead of throwing an exception if the method isn't found.

注意：代码使用spread syntax, not rest parameters.

const fn1 = undefined
const args = []
const fn2 = () => {}
const fn3 = () => {}

console.log(fn1?.(...args, fn2, fn3))

错误：

console.log(fn1?.(...args, fn2, fn3))
                                ^
TypeError: Function.prototype.apply was called on undefined, which is an undefined and not a function

Answer 1

有一些规则要遵循...剩余参数。

其中一条规则是 ...rest 参数只能是最后一个参数。

foo(...one, ...wrong, ...wrong)
foo(...wrong, bad, bad)
foo(ok, ok, ...correct)

参见：

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters

Answer 2

原来是V8的bug，提交了there，希望尽快修复

更新：it has been fixed.

可选链接 - Function.prototype.apply 被调用未定义，这是未定义的而不是函数

Optional Chaining - Function.prototype.apply was called on undefined, which is an undefined and not a function

javascript

google-chrome

v8

node.js

optional-chaining