roosteronacid roosteronacid - 3 months ago 24
Javascript Question

Handling specific errors in JavaScript (think exceptions)

How would you implement different types of errors, so you'd be able to catch specific ones and let others bubble up..?



One way to achieve this is to modify the prototype of the

Error
object:

Error.prototype.sender = "";


function throwSpecificError()
{
var e = new Error();

e.sender = "specific";

throw e;
}


Catch specific error:

try
{
throwSpecificError();
}

catch (e)
{
if (e.sender !== "specific") throw e;

// handle specific error
}




Have you guys got any alternatives?

CMS CMS
Answer

To create custom exceptions, you can inherit from the Error object:

function SpecificError () {

}

SpecificError.prototype = new Error();

// ...
try {
  throw new SpecificError;
} catch (e) {
  if (e instanceof SpecificError) {
   // specific error
  } else {
    throw e; // let others bubble up
  }
}

A minimalistic approach, without inheriting from Error, could be throwing a simple object having a name and a message properties:

function throwSpecificError() {
  throw {
    name: 'SpecificError',
    message: 'SpecificError occurred!'
  };
}


// ...
try {
  throwSpecificError();
} catch (e) {
  if (e.name == 'SpecificError') {
   // specific error
  } else {
    throw e; // let others bubble up
  }
}