Anonymous function: "object is not a function"

Question

Uncaught TypeError: object is not a function

I decided to make my writeMessage() function anonymous; before it would always mess up when another instance of the writeMessage() function was created at the same time, causing text output to be jumbled (both messages being "wrote" would get put together and mixed up).

However, I've seen to have run into an error (as shown above). The variable object is a jQuery object (e.g: $('#myDivElement')).

Any ideas as to why this is? Thanks.

function writeMessage(message,object){
    (function(message,object,i){
        var self = this;
        setTimeout(function(){
            if(i < message.length){
                object.append(message.substr(i,1));
                i++; 
                self(message,object,i);
            }
        }, 25);
    }(message,object,0));
}

Niet the Dark Absol · Accepted Answer · 2013-12-15 02:06:27Z

4

var self = this;

Since you are calling the function without context, self refers to the window object. window is an object (window.toString should give something like [object Window]) and not a function, so caling self(message,object,i) will not work.

Instead, use this:

var self = arguments.callee;

answered Dec 15, 2013 at 2:06

Niet the Dark Absol

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7 Comments

user3029571 Over a year ago

Ah, thank you! It's working perfectly now. Didn't realize the this keyword referred to the window object in an anonymous function.

jfriend00 Over a year ago

@user3029571 - The value of this has nothing to do with whether the function is anonymous or not. It has entirely to do with how the function is called and whether it's called in a way that sets this to something other than the global object. Since your function is not calling it in this way, this gets its default value.

cookie monster Over a year ago

@user3029571: Instead of arguments.callee you could also just give the function a name so that it'll work in strict mode where arguments.callee is prohibited.

Niet the Dark Absol Over a year ago

@cookiemonster But that defeats the purpose of an anonymous function, does it not? Strict mode is for wimps who can't write proper code without the browser noping their face :p

cookie monster Over a year ago

No it does not. There's no particular "purpose" for it to be anonymous when you actually want to reference it. That's why we give a function a name, isn't it? Using arguments.callee provides no advantage, and is less portable.

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