callback - JavaScript - Best practice to check is function -

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Before looking at the callback function I saw several ways to check the callback function.

1) 

  function (callback) {... if (callback! = Null) callback (); }

2) 

  function (callback) {... if (typeof callback == 'function') callBack (); }

3) 

  function (callback) {... if (callback! == empty) callback (); }

4) 

  function (callback) {... if (callback! = Undefined) callback (); }

5) 

  function (callback) {... try {callBack (); } Hold (mistake) {}}

6) 

  function (callback) {... if (callback & type (callback) == "function") callback (); }

7) 

  function (callback) {... if (callback) callback (); }

8) 

  function (callback) {... if (typeof window [callback] === 'undefined') callback (); }

9) 

  function (callback) {... if (callback instance of function) callback (); }

I believe there is more ...

What is the best way to check whether a given 'callback' parameter is a function or not? ? Why not use

P> and other examples?

if (callback! = Null)

Of course, why not notice there are still many non-function values ​​that pass it.

if (typeof callback == 'function')

the same You wish.

if (callback! == zero)

is not callback Undefined .

If (callback! = Undefined) does not work on

but do not see why null < / Code> is favorable (though equivalent).

try {callBack (); } Hold (mistake) {}

Uh, possibly slower in callback and swallowing mistakes. If you want the same, you should add it to one of the other tests.

If (callback and type (callback) == "function")

unnecessary, typeof may be faster than testing, if you care about performance then you want to test it, otherwise there is hardly any reason to be such a verb.

If (callback)

Sure, why not note that there are still many non-functional values ​​with integrity that Let's pass it.

if (type window [callback] === 'undefined')

not completely enough It is a different thing.

If (callback instance of function)

This should work for everything, but some extreme torrent cases, But using the typeof is safe (faster and faster).


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