[dojo-contributors] Stance on custom error types

Mark Wubben mark at novemberborn.net
Mon Jun 4 08:41:26 EDT 2012

Dojo seems to do custom errors by adding a `dojoType` property to the error instance. Examples in `dojo/request` and `dojo/io`. The new Promise code however uses a subclassed Error.


	function CancelError(message){
		Error.captureStackTrace && Error.captureStackTrace(this, CancelError);
		this.message = message || "The deferred was cancelled.";
		this.name = "CancelError";
	CancelError.prototype = new Error;
	CancelError.prototype.constructor = CancelError;
	return CancelError;

I prefer subclassed errors because they're easier to instantiate and test for (either using `instanceof` or checking their `name`). We could even add `dojoType` properties.

What is your preference?

In any case, we need to standardize these across the codebase.

Mark Wubben


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