Proper use of errors

Question

I\'m using TypeScript for a reasonably large project, and am wondering what the standard is for the use of Errors. For example, say I hand an index out of bounds ex

Answer 1

The convention for out of range in JavaScript is using RangeError. To check the type use if / else + instanceof starting at the most specific to the most generic

try {
    throw new RangeError();
}
catch (e){
    if (e instanceof RangeError){
        console.log('out of range');
    } else { 
        throw; 
    }
}

Answer 2

Someone posted this link to the MDN in a comment, and I think it was very helpful. It describes things like ErrorTypes very thoroughly.

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".

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 de-referencing 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.

Answer 3

Don't forget about switch statements:

• Ensure handling with default.
• instanceof can match on superclass.
• ES6 constructor will match on the exact class.
• Easier to read.

function handleError() {
    try {
        throw new RangeError();
    }
    catch (e) {
        switch (e.constructor) {
            case Error:      return console.log('generic');
            case RangeError: return console.log('range');
            default:         return console.log('unknown');
        }
    }
}

handleError();

Answer 4

Simple solution to emit and show message by Exception.

try {
  throw new TypeError("Error message");
}
catch (e){
  console.log((<Error>e).message);//conversion to Error type
}

Caution

Above is not a solution if we don't know what kind of error can be emitted from the block. In such cases type guards should be used and proper handling for proper error should be done - take a look on @Moriarty answer.