javascript DOMException Description

The job of conveying the DOM exception information to a scripter falls to the hosting environment, rather than the DOM. Because JavaScript 1.5 already has an exception handling mechanism, the task of blending the DOMException system with JavaScript exception handling fell first to Netscape, as implemented in Netscape 6. The new mechanism permits different kinds of error objects to circulate through the exception handling operations, thus leaving the original system intact, while extending the mechanism to accommodate not only the W3C DOM DOMException object, but some Netscape-specific errors, as well. Processing of exceptions of all kinds continues to take place in the catch block of a try/catch construction, and all information about the exception is still passed as an object through a single parameter to the catch block.

Netscape's DOM exception object (which embodies the W3C DOMException object) arrives at the catch block with a longer list of properties and methods associated with it than does an exception arising from other causes (e.g., trying to use a JavaScript variable that has not been initialized). The distinguishing property of a DOMException object, missing from the other types, is the code property. Moreover, any code value between 1 and 15 indicates an exception type known to the formal DOM specification through Level 2. Others will certainly be added to the list in the future. Netscape uses code numbers starting with 1000 for its list of browser-specific exceptions.

If you wish to process true W3C DOM exceptions along their own execution path, you can use a construction similar to the following (which allows for the DOMException list to grow to 999 in future iterations):

try {
    // your DOM-related statement goes here
}
catch(e) {
    if (typeof e.code == "number") {
        if (e.code< 1000) {
            // process DOMException object here
        } else {
            // process Netscape DOM exception object here
        }
    } else {
        // process language or other exceptions here
    }
} 

Of course, it is highly unlikely that exception details will be of benefit to users, but they are invaluable to you during development. For more on exception handling, see the error object.

code

None.

None.