I'm wondering about snippet of code you have used

[saadshahd]

I'm wondering about your reasons of using this mechanism instead of the regular typeof, instanceof.
_Just I want to learn from you_, I've tried to search about differences my self but I got no thing.

[royling]

I got the same question. Though I've already read about your thinking about one-line module, I really did not understand why an npm module is required for this thing. IMHO, it's more simple to just put it as typeof fn === 'function' or something similar?

[saadshahd]

@royling I'm not wondering about the one-line node module.

The question here why:
toString.call(x) === '[object Function]'
not:
typeof x === 'function'
nor:
x instanceof Function

[royling]

ok, got your point.

[sindresorhus]

This is what Lodash, Underscore and jQuery does. In modern environments typeof is good enough, but in older browsers (even Safari 8) and PhantomJS there are bugs and calling the internal [[Class]] directly Object.prototype.toString.call() works around that. I guess this is not useful in Node.js though, so I added a note 3d25982.

You should not use instanceof though as it won't work if the function comes from another realm, e.g. another frame or window, in the browser.

Read more here: http://javascript.info/tutorial/type-detection

[daryl]

Interesting, thanks for clearing it up.

[saadshahd]

@sindresorhus Thanks, for clarifying the differences.