Javascript: Exception and error strategy

Question

Hello,

Does anybody know a good strategy for handling exceptions and errors. At the moment I have different pieces of code handling their own validation/errors/exception but I would really have a centralized strategy. I was thinking of some global notification system that passes some errors/exceptions to the user like validation. Other errors I would post to my back-end and log them.

For example a validation error could contain the element that caused the error. That way I can add a class to highlight it and append some text before or after.

So if anybody has some concrete examples on how to do this I would really appreciate it.

Answer 1

If your main problem is about validation I think the most concrete way to go about it would be to use the jQuery validation plug-in which is truely customizable and has a good base for your to start handling exceptions.

I am not a big fan of try catch blocks in javascript but I think also you can start from giving particular codes for your self to different errors and handle them in switch case blocks.

Answer 2

If it's worth it, you could customize errors and build a function around these which contains default behaviour:

function errorHandler() {

    var error = arguments[1] ; //!! pass the error
    /* additional arguments */

    var errorCode = error.message ;

    var errorMap = { //!! a map that matches error codes to default behaviour
        "customErrorName":function() {
            /* default behaviour for this kind of error */
        } ,
        /* more custom error codes and default behaviour */
    }

        if(errorCode in errorMap) { //!! error code has a default behaviour
            errorMap[ errorCode ]() ; //!! call default behaviour
        } else {
            /* log unknown error */
        }

}

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You would implement this in a try { ... } catch(e) { ... } block:

try {
    /* your code */
    if(someErrorCondition) {
        throw new Error("someError") ;
    }
} catch(e) {
    errorHandler(e) ;
}

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There are default error types in javascript too. There's a list in the following link: https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Error