JavaScript Error Handling Error types


Example

There are six specific core error constructors in JavaScript:

  • EvalError - creates an instance representing an error that occurs regarding the global function eval().

  • InternalError - creates an instance representing an error that occurs when an internal error in the JavaScript engine is thrown. E.g. "too much recursion". (Supported only by Mozilla Firefox)

  • RangeError - creates an instance representing an error that occurs when a numeric variable or parameter is outside of its valid range.

  • ReferenceError - creates an instance representing an error that occurs when dereferencing an invalid reference.

  • SyntaxError - creates an instance representing a syntax error that occurs while parsing code in eval().

  • TypeError - creates an instance representing an error that occurs when a variable or parameter is not of a valid type.

  • URIError - creates an instance representing an error that occurs when encodeURI() or decodeURI() are passed invalid parameters.

If you are implementing error handling mechanism you can check which kind of error you are catching from code.

try {
    throw new TypeError();
}
catch (e){
    if(e instanceof Error){
        console.log('instance of general Error constructor');
    }

    if(e instanceof TypeError) {
        console.log('type error');
    }
}

In such case e will be an instance of TypeError. All error types extend the base constructor Error, therefore it's also an instance of Error.

Keeping that in mind shows us that checking e to be an instance of Error is useless in most cases.