Is there a way to handle undefined functions being called in JavaScript?

Question

If I have a function like the following:

function catchUndefinedFunctionCall( name, arguments )
{
    alert( name + ' is not defined' );
}

and I do something silly like

foo( 'bar' );

when foo isn't defined, is there some way I can have my catch function called, with name being 'foo' and arguments being an array containing 'bar'?

npup · Accepted Answer · 2010-03-27 00:25:33Z

10

There is in Mozilla Javascript 1.5 anyway (it's nonstandard).

Check this out:

var myObj = {
    foo: function () {
        alert('foo!');
    }
    , __noSuchMethod__: function (id, args) {
        alert('Oh no! '+id+' is not here to take care of your parameter/s ('+args+')');
    } 
}
myObj.foo();
myObj.bar('baz', 'bork'); // => Oh no! bar is not here to take care of your parameter/s (baz,bork)

Pretty cool. Read more at https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Object/NoSuchMethod

answered Mar 27, 2010 at 0:25

npup

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3 Comments

Emory Over a year ago

This is very cool and nearly exactly what I was looking for - is there an equivalent that works in IE 6+?

Loïc Over a year ago

As of december 2015, this is an obsolete function that shouldn't be used anymore.

ery245gs Over a year ago

@Loïc what should be used then?

alex · Accepted Answer · 2010-03-27 00:40:02Z

6

try {
 foo();
}
catch(e) {
   callUndefinedFunctionCatcher(e.arguments);
}

UPDATED

passing e.arguments to your function will give you what you tried to pass originally.

edited Mar 27, 2010 at 0:40

alex

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answered Mar 26, 2010 at 23:48

Levi Hackwith

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4 Comments

Andy E Over a year ago

arguments is not a property of the Error object, it is a property of functions. In your example e is an error object and so e.arguments will be undefined.

npup Over a year ago

I think it is just that kind of checking the catch-all strategy people want to get away from.

Levi Hackwith Over a year ago

I just ran the following in chrome: try { bar('foo'); } catch(e){ alert(e.arguments); for(x in e) { alert(x) } } it alerts 'foo' and then alerts 'arguments' as a property of e. Am I crazy? Or just still wrong?

Carlos Morales Over a year ago

doing try/catch in JS is not always a good idea, specially if there are async functions inside the block. Check stackoverflow.com/questions/3677783/…

user216441 · Accepted Answer · 2010-03-26 23:46:56Z

0

someFunctionThatMayBeUndefinedIAmNotSure ? someFunctionThatMayBeUndefinedIAmNotSure() : throw new Error("Undefined function call");

answered Mar 26, 2010 at 23:46

user216441

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