jQuery Forum

your proposal in IE
var s = "this is a string with function word";
isFunction(s) // true
cool!!!
now, re-consider that we all like reliable code and your code as is is the less reliable ever for its purpose in IE. I gonna probably create a post in WR 'cause where you think "small and simple is better" here we have to deal with big application that should never fail ( at least that's my job ) so a bit more code to be as sure as possible is not an option for me.
Regards

jQuery had that sort of checks and fairly dumped them in 1.3:
http://docs.jquery.com/Release:jQuery_1.3#Changes
> .isFunction is simpler now, it no longer handles some strange edge cases (in favor of simplicity and performance).
By the way, ‘x instanceof Function’ leaks for window and DOM objects
in IE.
http://ajaxian.com/archives/working-aroung-the-instanceof-memory-leak

All Salsa isFunction and isIENativeFunction
<a href="http://webreflection.blogspot.com/2009/08/isfunction-or-isienativefunction.html">http://webreflection.blogspot.com/2009/08/isfunction-or-isienativefunction.html</a>
Both proposal, you decide ;-)
Best Regards

Indeed, we dropped this consciously and we don't plan to re-add it.
--
Ariel Flesler

Ariel not sure you read my post already, what I am talking about is an isIECallable function that could be a part from isFunction (I used isIENativeFunction but it does not matter the name, it can be only less than 100 characters and nothing else)
Regards

I was actually replying to Azat but yes, I read your post.
Your code is cool, not that different from the one we had back then,
written by John.
The thing is, how often would you actually call isFunction on alert(,
confirm, etc) or a DOM element's method. You certainly won't be
passing those as a function argument too often, is it really worth the
overhead, bytes, etc ?
--
Ariel Flesler

Worryingly in IE8 this is the "state of play" :
// IE8
Object.prototype.toString(Error.valueOf)
/* [object Object] */
typeof Error.valueOf
/* function */
JavaScript Error is not DOM object. Is this an "edge case" or not?
Anyway, I posted too fast, the version bellow works.
( function () {
// GPL (c) 2009 by DBJ.ORG
isFunction = typeof (top.alert) === "object" ?
function(x) {
switch (typeof x) {
case "function" : return true ;
case "object" : return (x + "").match(/
function/) !== null ;
default : return false ;
}
}
: /* non IE browsers use this */
function (x) {
return x instanceof Function;
}
})()
@Azat : "By the way, ‘x instanceof Function’ leaks for window and DOM
objects in IE. " ...
True. But above "instanceof" is used only in non-IE browsers.
--DBJ

instanceof won't worik because a function within an iframe won't have
the same constructor as one outside of it.

@James
Thanks for this. This is why actually never use 'instanceof' myself.
I always rely on :
Object.prototype.toString.call(Function()) === "[object Function]"
same as jQuery, prototype.js, Dojo, etc ...
Inspired bu recent "isObject" discussion here I have posted this :
http://dbj.org/dbj/?p=270
Where I have presented a little framework and (hopefully) clarified
the terminology, too ...
Althouhg over there I have decided to ignore this IE issue , which I
am hopefully solving here..
I should really stop posting while working, so here is V3 ;o)
( function () {
// GPL (c) 2009 by DBJ.ORG
isFunction = typeof (top.alert) === "object"
? /* IE will use this */
function(x) {
switch (typeof x) {
case "function" : return true ;
case "object" : return (x + "").match(/
function/) !== null ;
default : return false ;
}
}
: /* non IE browsers use only this */
function (x) {
return Object.prototype.toString.call(x) === "[object
Function]" ;
}
})()
--DBJ

On Aug 4, 10:04 am, DBJDBJ

@Henry : you are right ... I really should stop frequent postings ...
// IE8
Object.prototype.toString.call(Error.valueOf)
/*
[object Function]
*/
typeof Error.valueOf
/*
function
*/

V4 ;o)
Is this not the simplest working solution ?
// GPL (c) 2009 by DBJ.ORG
function isFunction(x) {
switch (typeof x) {
case "function" : return true ;
case "object" : return (x + "").match(/
function/) !== null ;
default : return false ;
}
}
isFunction( top.alert )
/*
true
*/
isFunction( isFunction )
/*
true
*/

On Aug 4, 4:34 pm, DBJDBJ

2009/8/4 DBJDBJ <dbjdbj@gmail.com>:

I think my first reply was basically the same after another in the old post, apparently DBJ does not get it. DBJ, more coffee! ;-)

On Aug 4, 11:03 am, Henry <rcornf...@raindrop.co.uk>

V.5 ?!
Here is the (hopefully) proper verion :
// GPL (c) 2009 by dbj.org
function isFunction (x) {
switch(typeof x) {
case "function" : return true ;
case "object" :
if ( "function" !== typeof x.toString )
return (x + "").match(/function/) !==
null ;
else
return Object.prototype.toString.call
(x) === "[object Function]" ;
break ;
default : return false ;
}
}
// this was breaking the previous version
window.test = {
toString: function() { return '[function]'; }
};
isFunction( test )
/*
false
*/
isFunction( isFunction )
/*
true
*/
isFunction( confirm )
/*
true
*/

var o = {valueOf:function(){return "[function]"},toString:null};
alert(isFunction(o)); // true in IE
DBJ what is the problem, really? I wrote two options and both do what you are trying to di with hundreds of tests ... is it that difficult?
<span style="font-family: courier new,monospace;">var isFunction = (function(toString){</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">    var s = toString.call(toString),</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        u = typeof u;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">    return typeof this.alert === "object" ?</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        function(f){</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">            return s === toString.call(f) || (!!f && typeof f.toString == u && /^\s*\bfunction\b/.test(f));</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        }:</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        function(){</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">            return s === toString.call(f);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    ;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">})(Object.prototype.toString);</span>
Regards

Sorry, forgot an argument ...
<span style="font-family: courier new,monospace;">var isFunction = (function(toString){</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">    var s = toString.call(toString),</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        u = typeof u;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">    return typeof this.alert === "object" ?</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        function(f){</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">            return s === toString.call(f) || (!!f && typeof f.toString == u && /^\s*\bfunction\b/.test(f));</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        }:</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        function(f){</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">            return s === toString.call(f);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    ;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">})(Object.prototype.toString);</span>
LOL, regards

Actually, that object could hack mine as well so, this is my definitive solution.
<span style="font-family: courier new,monospace;">var isFunction = (function(toString){</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    var s = toString.call(toString),</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        u = typeof u;</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    return typeof this.alert === "object" ?</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        function(f){</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">            return s === toString.call(f) || (!!f && typeof f.toString == u && typeof f.valueOf == u && /^\s*\bfunction\b/.test(f));</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">        }:</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        function(f){</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">            return s === toString.call(f);</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">        }</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    ;</span><br style="font-family: courier new,monospace;"><span style="font-family: courier new,monospace;">})(Object.prototype.toString);</span>
Regards

I am not that confident as Andrea, but bellow might be a "definitive"
solution too ;o)
function isFunction (x) {
switch(typeof x) {
case "function" : return true ;
case "object" :
if (( "function" !== typeof x.toString ) &&
( "function" !== typeof x.valueOf ))
return (x + "").match(/function/) !==
null ;
else
return Object.prototype.toString.call
(x) === "[object Function]" ;
break ;
default : return false ;
}
}
var breaker = {valueOf:function(){return
"[function]"},toString:null};
isFunction(breaker)
/*
false
*/
With IMHO less obfuscations ...

If anybody is interested , I have posted a good natured reply here :
https://www.blogger.com/comment.g?blogID=34454975&postID=1742136638108479551&page=1
Although by now, I think only the most persistent readers have
persisted reading this thread ...
--DBJ