How to check if a JS function is defined?

[laredotornado]

Hello,

What is a cross-browser way to check if a function has been defined?

It seems that this code

if (myFn) {
myFn();
}

executes whether myFn is defined or not. When it is not, a JS error
results.

Your help is greatly appreciated, - Dave

[Ivo]

<la***********@zipmail.com> wrote

What is a cross-browser way to check if a function has been defined?
It seems that this code

if (myFn) {
myFn();
}

executes whether myFn is defined or not. When it is not, a JS error
results.

I don't see how that seems, but have you tried this if statement:
if ( typeof myFn==='function' )
--
ivo
http://4umi.com/web/javascript/

[RobG]

la***********@zipmail.com wrote:

Hello,

What is a cross-browser way to check if a function has been defined?

It seems that this code

if (myFn) {
myFn();
}

executes whether myFn is defined or not. When it is not, a JS error
results.

Use typeof:

function someFn(){}

function isFn(funcRef)
{
return 'function' == typeof funcRef;
}

alert('Is someFn a function? ' + isFn(someFn) );

--
Rob

[Thomas 'PointedEars' Lahn]

RobG wrote:

la***********@zipmail.com wrote:

What is a cross-browser way to check if a function has been defined?
[...]

Use typeof:

function someFn(){}

function isFn(funcRef)
{
return 'function' == typeof funcRef;
}

alert('Is someFn a function? ' + isFn(someFn) );

Note that for host object's methods the `typeof' operation may evaluate to
"object" as well.
PointedEars