Question

The code below throws an exception in firefox:

 $(function(){
        $(["one","two","three"]).each(function(){
            if(this == "one")
                $("div#msg").html(this);
        });
    });

the exception is this:

Could not convert JavaScript argument arg 0 [nsIDOMDocumentFragment.appendChild]

Yet if I change code and use this.toString() as follows, it works:

$(function(){
    $(["one","two","three"]).each(function(){
        if(this == "one")
            $("div#msg").html(this.toString());
    });
});

If “this” is a string, why do I need to do toString()? Is there a nuance of javaScript which I am missing or am I just being a moron? Please tell me it’s a nuance.

Answer 1

Distinction between string primitives and String objects JavaScript automatically converts primitives and String objects, so that it’s possible to use String object methods for primitive strings. In contexts where a method is to be invoked on a primitive string or a property lookup occurs, JavaScript will automatically wrap the string primitive and call the method or perform the property lookup.

~From MDN Read More

$("div#msg").html("one"); //works

$("div#msg").html(new String("one")); // doesnt work

For ex:

try {         
    $("div#msg").html(new String("one"));
} catch (e) {
    $("div#msg").html("Can't use String object");
}

And the output of the div is Can't use String object. Demo here