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Question

Javascript Try/Catch

Answer 1

+5 A:

The problem is with this line:

var grep = new RegExp('gr[');

'[' is a special character so it needs to be escaped. Also this line is not wrapped in try...catch, so you still get the error.

Edit: You could also add an

alert(e.message);

in the catch clause to see the error message. It's useful for all kind of errors in javascript.

Edit 2: OK, I needed to read more carefully the question, but the answer is still there. In the example code the offending line is not wrapped in the try...catch block. I put it there and didn't get errors in Opera 9.5, FF3 and IE7.

rslite 2008-09-23 12:37:39

You've missed the question itself

Teifion 2008-09-23 12:41:09

Yeah, I've seen that now in Paul's answer. It was a simple case of me being extra stupid. Thanks for the help anyway :)

Teifion 2008-09-23 12:49:06

Answer 2

+1 A:

your RegExp doesn't close the [

In my FireFox, it never returns from the constructor -- looks like a bug in the implementation of RegExp, but if you provide a valid expression, it works

Lou Franco 2008-09-23 12:38:15

As with rslite, you've missed the actual question, I want to find a way to run such a regex and catch the resultant error

Teifion 2008-09-23 12:43:15

Answer 3

+13 A:

Try this the new RegExp is throwing the exception

Regex

    <script type="text/javascript" charset="utf-8">
            var grep;

            try {
                    grep = new RegExp("gr[");
            }
            catch(e) {
                    alert(e);

            }
            try
            {
                    var results = grep.exec('bob went to town');
            }
            catch (e)
            {
                    //Do nothing?
            }

            alert('If you can see this then the script kept going');
    </script>

Paul Whelan 2008-09-23 12:42:05

Answer 4

A:

One option is to validate the user-generated expressions. That is; escape characters that you know will stall your script.

roosteronacid 2008-09-23 12:54:04

Answer 5

+4 A:

var grep, results;

try {
    grep = new RegExp("gr[");
    results = grep.exec('bob went to town');
}
catch(e) {
    alert(e);
}
alert('If you can see this then the script kept going');

Jim 2008-09-23 12:55:55

Answer 6

+1 A:

putting the RegExp initialization inside the try/catch will work (just tested in FireFox)


var grep, results;

try
{
    grep = new RegExp("gr["); // your user input here
}
catch(e)
{
    alert("The RegExpr is invalid");
}

// do your stuff with grep and results

Escaping here is not the solution. Since the purpose of this snippet is to actually test a user-generated RegExpr, you will want to catch [ as an unclosed RegExpr container.

Filini 2008-09-23 15:37:29

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