> Le 24 janv. 2017 à 19:12, Isiah Meadows <[email protected]> a écrit :
>
> To clarify, I'm wanting to know if it's a callable that isn't a class.
> Technically, I could use `Function.prototype.toString` for most
> practical purposes of mine, but that'd be super slow (I'd need it in a
> warm loop), and wouldn't catch native construct-only classes like `Map`
> and `Set` (which are still `typeof f === "function"`).
>
> ```js
> var funcToString = Function.prototype.toString
>
> function isCallable(f) {
> return typeof f === "function" &&
> /^\s*class(\s*\{|\s+[^(])/.test(funcToString.call(f))
> }
> ```
Your `isCallable` function has a flaw: it will treat differently:
```js
// ES6 class
class Foo {
constructor() {
// ...
}
}
```
and:
```js
// pre-ES6 almost-compatible approximation of a class
function Foo() {
if (!(this instanceof Foo))
throw new TypeError("Foo must be invoked with 'new'");
// ...
}
```
You are unable to guess that a function defined with the `function` keyword is
intended to be a constructor or a function.
—Claude
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