如何检索尝试/捕获错误

Question

how can I find the error

try {
    undef
} catch (e){
    console.log(e)
    console.dir(e)
}

the information bust be there somewhere, because the console.log (in firebug) includes:

ReferenceError: undef is not defined

but when I browse the e object, I can't find it.

How do I find out what the error is programmatically, so I can handle the error accordingly?

Edit:

Answer 1

try {

    if(typeof undef  == 'undefined'){       
        console.log('We should not access this "undef" var');
    }       
    console.log('The next line will produce an exception');
    undef
} catch (e){
    console.log(e);
    for(index in e){
        console.log(index+' ('+(typeof e[index])+'): '+ e[index]);
    }
}

---

Which will produce:

---

We should not access this "undef" var
The next line will produce an exception
ReferenceError: undef is not defined
fileName (string): file:///B:/xampp/htdocs/study/test.html
lineNumber (number): 12
stack (string): @file:///B:/xampp/htdocs/study/test.html:12

Answer 2

I don't think you can pull its type explicitly, but you can test it:

try {
    undef
} catch (e){
    console.log(e)
    console.dir(e)
    if(e instanceof ReferenceError) {
      console.log("Ooops! Fat fingers!");
    }
}

Answer 3

But of trial and error gives me this...

try {
    undef
} catch (e){
    console.log(e.toString())
    // ReferenceError: undef is not defined
}

I guess firebug is just accessing the .toString() method of e

---

Edit:

I am guessing the .toString() method just concatenates the only two properties that are guaranteed cross browser - name and message - so I think e.message is the only reliable and useful piece of information to go with.