V8's equivalence of SpiderMonkey's catch(e if e..)

Question

Using SpiderMonkey you can utilize conditional catch blocks to route exceptions to the appropriate handler.

try {
// function could throw three exceptions
getCustInfo("Lee", 1234, "lee@netscape.com")
}
catch (e if e == "InvalidNameException") {
// call handler for invalid names
bad_name_handler(e)
}
catch (e if e == "InvalidIdException") {
// call handler for invalid ids
bad_id_handler(e)
}
catch (e if e == "InvalidEmailException") {
// call handler for invalid email addresses
bad_email_handler(e)
}
catch (e){
// don't know what to do, but log it
logError(e)
}

example from MDN

However in V8 this code wont compile, any suggestions, or work arounds other than the obvious.

score 6 · Accepted Answer · answered Jan 08 '11 at 18:42

6

There's no similar feature in the other JavaScript engines as far as I know.

But it is easy to convert code using this feature:

try {
    A
} catch (e if B) {
    C
}

into code that just uses standard features that all the JavaScript engines support:

try {
    A
} catch (e) {
    if (B) {
        C
    } else {
        throw e;
    }
}

The example you gave is even easier to translate:

try {
    getCustInfo("Lee", 1234, "lee@netscape.com");
} catch (e) {
    if (e == "InvalidNameException") {
        bad_name_handler(e);
    } else if (e == "InvalidIdException") {
        bad_id_handler(e);
    } else if (e == "InvalidEmailException") {
        bad_email_handler(e);
    } else {
        logError(e);
    }
}

answered Jan 08 '11 at 18:42

Jason Orendorff

42,793
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1

Will that the obvious thing, a switch statement maybe even better, your sure there is no similar implementations? – Amjad Masad Jan 08 '11 at 18:51
Yes. It's a nonstandard extension in SpiderMonkey. – Jason Orendorff Jan 10 '11 at 15:19
Side Note: this does not handle things like stack traces if you want to not catch an exception of a certain type. – Benjamin Gruenbaum Nov 05 '13 at 16:37

V8's equivalence of SpiderMonkey's catch(e if e..)

1 Answers1