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POWhat's the best way to expose and compose errors in Node.js?
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  1. POWhat's the best way to expose and compose errors in Node.js?
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    copied!<p>I'm writing a module that talks to a REST API, and since the REST API provides nice, semantic error responses (e.g. 403 vs. 503), I want to convey those semantic errors to callers.</p> <p>(Edit: what I mean by that is, the caller should be able to programmatically understand the cause of the error and act accordingly, e.g. display the appropriate UI.)</p> <p>What's the best way for me to do so?</p> <ol> <li><p>Create my own <code>Error</code> subclasses for those semantics, e.g. <code>mymodule.ForbiddenError</code>, <code>mymodule.ServiceUnavailableError</code>? Callers would then check <code>instanceof</code> to derive semantics. This is most typical in statically-typed languages like C# and Java.</p></li> <li><p>Add e.g. a <code>mymoduleCode</code> property to standard <code>Error</code> instances, with semantic strings like <code>'Forbidden'</code> or <code>'ServiceUnavailable'</code>. Node.js itself does this, e.g. <code>code: 'ECONNREFUSED'</code>.</p></li> <li><p>Some other way?</p></li> </ol> <p>==</p> <p>I'm writing another module now, that wraps the first module. I don't want to expose the internal module's errors directly, but it'd be nice to compose/wrap them, for debuggability.</p> <p>What's again the best way for me to do so?</p> <ol> <li><p>Add e.g. an <code>internalError</code> property to my <code>Error</code> instances that references the internal module's <code>Error</code> instance. Again C# and Java do this. (<a href="http://msdn.microsoft.com/en-us/library/system.exception.innerexception%28v=vs.110%29.aspx">Exception#InnerException</a> / <a href="http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/Throwable.html#getCause%28%29">Throwable#cause</a>)</p></li> <li><p>Some other way?</p></li> </ol> <p>Most tooling I've seen, though, only displays the <code>stack</code> property of <code>Error</code> instances, so this data would get lost in those cases. Is there a typical/conventional way that already exists?</p>
 

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