Using and catching RangeError in javascript

Question

I'm about to throw an exception using RangeError and wanted to check that I'm using it correctly and how to best catch it.

I have a function that could throw a RangeError OR a TypeError like this

function saveNumber(val) {
  // Only accept numbers.
  if (typeof val !== 'number') {
    throw new TypeError();
  }

  // Error if the number is outside of the range.
  if (val > max || val < min) {
    throw new RangeError();
  }

  db.save(val);
}

I'd like to call it and only deal with the RangeError. What's the best way to do this?

another piece of code may want to call this function and deal with the TypeError — eddiec
– eddiec, Commented Dec 3, 2013 at 15:45

Community · Accepted Answer · 2017-05-23 11:54:53Z

12

try {
  saveNumber(...);
} catch (e) {
  if (e instanceof TypeError) {
    // ignore TypeError
  } 
  else if(e instanceof RangeError) {
    // handle RangeError
  }
  else {
    // something else
  } 
}

source

edited May 23, 2017 at 11:54

CommunityBot

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answered Dec 3, 2013 at 15:47

qwertynl

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1 Comment

Roly Over a year ago

In general you need to re-throw if you don't handle.

Snake Eyes · Accepted Answer · 2018-10-31 14:30:18Z

3

Straight from the MDN documentation on try - catch:

try {
    saveNumber(...);
} catch (e is instanceof RangeError) {
    // Do something
} catch (e) {
    // re-throw whatever you don't want to handle
    throw e;
}

edited Oct 31, 2018 at 14:30

Snake Eyes

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answered Dec 3, 2013 at 15:48

Justin Niessner

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2 Comments

eddiec Over a year ago

JS Hint is complaining 'catch filter' is only available in Mozilla JavaScript extensions (use moz option)'. So it's a nice answer but not fully compatible.

Pavlo Over a year ago

From the same docs: "Reminder: this functionality is not part of the ECMAScript specification."

Anona112 · Accepted Answer · 2017-10-24 10:27:10Z

2

slightly more elegant answer:

switch (error.constructor) {
    case NotAllowedError:
        return res.send(400);
    case NotFoundError:
        return res.send(404);
    default:
        return res.send(500);
}

answered Oct 24, 2017 at 10:27

Anona112

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