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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Object.defineProperties
Date: Sun, 07 May 2017 17:11:04 +0200
Organization: PointedEars Software (PES)
Lines: 54
Message-ID: <1783967.oMNUckLgyt@PointedEars.de>
References: <oebtq0$2611$1@csiph.com> <objects-20170503082342@ram.dialup.fu-berlin.de> <oec3h1$2dav$1@csiph.com> <1943190.NgBsaNRSFp@PointedEars.de> <oeid9d$1ag1$1@csiph.com> <1592229.TLkxdtWsSY@PointedEars.de> <oekitc$2tgv$1@csiph.com> <oelc5o$4iv$1@news.albasani.net> <oeldrk$j52$1@csiph.com> <38321860.ZmDeoRnzTM@PointedEars.de> <oemj5r$1frd$1@csiph.com>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
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Xref: csiph.com comp.lang.javascript:33249

Cezary Tomczyk wrote:

> On 07/05/2017 02:37, Thomas 'PointedEars' Lahn wrote:
>> Cezary Tomczyk wrote:
>>>      function isTypeOf(obj, typeToCheck) {
>>>          var type;
>>>
>>>          if (arguments.length < 2) {
>>>              throw new Error('[isTypeOf] requires two arguments');
>>>          }
>>
>> You should throw a TypeError or a custom-typed exception (I throw
>> object.js:jsx.InvalidArgumentError for such).
> 
> Nice tip. I will use:
> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
> 
> However, optional argument 'lineNumber' there is a bit weird to me as I
> don't know where the specified fragment of code will be in a production
> version (after minification) and therefore I can't pass there a line
> number.

It is optional and proprietary anyway.

But, if available, you can obtain the URI and line number from the “stack” 
property and set them later.  (This is where custom-typed exceptions come 
in.)
 
>> The message is confusing (“Is ‘isTypeOf’ the element of a one-element
>> array?”)
> 
> The purpose of that message is to tell you where the message happened,
> here the '[isTypeOf]' refers to function name, and what happened, here
> is a message that 'requires two arguments'.

I *know* what it is *supposed* to tell.  It is nevertheless confusing to the 
person reading it.  The message should not require such an explanation.

It should also say more than “requires two arguments” because the next 
question of the developer would be “What arguments does it require, then?”.

See also jsx.InvalidArgumentError; currently

<https://github.com/PointedEars/JSX/blob/master/object.js#L3924-L3947>

Usage example:

<https://github.com/PointedEars/JSX/blob/master/object.js#L2669-L2671>
 
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