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Re: Inserting stuff received with AJAX into the DOM

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On 21/08/2017 22:16, Thomas 'PointedEars' Lahn wrote:
> Cezary Tomczyk wrote:
> 
>> On 21/08/2017 17:47, Thomas 'PointedEars' Lahn wrote:
>>> Cezary Tomczyk wrote:
>>>> On 21/08/2017 16:44, Thomas 'PointedEars' Lahn wrote:
>>>>> Cezary Tomczyk wrote:
>>>>>> I am sure that:
>>>>>>
>>>>>> const par = document.createElement( 'p' );
>>>>>>
>>>>>> will always create HTML element. I can't see any real scenario where
>>>>>> createElement method will return "something else than a reference to
>>>>>> an object that has a method named “appendChild”" in that particular
>>>>>> scenario.
>>>>>
>>>>> Why?
>>>>
>>>> https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement
>>>> […]
>>> Certainly you can come up with something better than hearsay.
>>
>> Possibly there is a better explanation than just hearsay.
> 
> Possibly.  Can you come up with it?

No. I was expecting you'll do that.

>>>> In that particular case:
>>>>
>>>> const par = document.createElement( 'p' );
>>>>
>>>> this will return an HTML p element.
>>>
>>> It may.
>>
>> Well, recently you wrote:
>>
>> "As a rule of thumb, if the object in question always had the method and
>> it always worked, I do not feature-test it."
>>
>> Isn't now that case?
> 
> This is not about not feature-testing the createElement() method.  It is
> about testing its return value before using that.

Got it, but still I claim that in that particular case I would not test it.

>> I might be wrong, but if there are cases that may strongly require "if"
>> here then I'd like to know.
> 
> You are trying to shift the burden of proof again.  You have claimed that
> this method can never return something unsuitable.  So how do *you* support
> that claim *other* than with hearsay from MDN (I called it “hearsay” because
> it is a wiki and there is no other reference attached to your claim)?

> You have claimed that this method can never return something unsuitable.

Let me clarify it: it may return something unexpected, but I've never 
tested return value from createElement method before I use it because 1) 
it was always working as expected and 2) I haven't got any scenario 
where I could say it's required.

>>>> I would say and even, if it'll occur then calling "appendChild" later
>>>> will throw a DOM exception which I think it's good because it helps to
>>>> catch the error on an early stage.
>>> An exception, but not a “DOM exception” will be thrown, if the object
>>> does not have the method.  Or execution will simply stop with an error.
>>> Who knows.  createElement() is a host object’s method.
>>
>> Right, an exception.
> 
> So, what if no exception is being thrown by a method, would you not want to
> make sure as best as you can that the return value of a method is actually a
> reference to an object, before you attempt to access its properties?

Generally yes, but as for the returns from createElement method I do not 
do that.

>> createElement() is a host object’s method, but it was always available
> 
> This is simply not true.  Maybe you are too young to know it:
> 
> Before the W3C DOM, which became a W3C Recommendation in 1998 CE (and was
> quickly adopted through Mozilla 1.0 in 2000), there have been element
> objects that did not have that method because it was introduced with the
> aforementioned API.
> 
> In what was called “Dynamic HTML” (DHTML) at the time, in Netscape Navigator
> (and later, Communicator) 4.x, there were layer objects for `LAYER` (and
> IIRC, `DIV`) elements whose content you could replace by calling their
> write() method; and in Internet Explorer and other MSHTML-based user agents
> there were element objects which had only the “innerHTML” and “outerHTML”
> properties, and several other methods (like insertAdjacentHTML() recently
> mentioned by Martin) for this instead.
> 
>> and unless it's not modified it has been always working quite good.
> 
> Based on what *data*?

Own experience.

I'd rather strongly urge to give me a scenarios where createElement 
method returns something different than created HTML element. I'd like 
to understand why do I need to test a return value of createElement 
method if it's actually a reference to an object, before I attempt to 
access to it's properties.

-- 
Cezary Tomczyk
http://www.ctomczyk.pl/

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Inserting stuff received with AJAX into the DOM bit-naughty@hotmail.com - 2017-08-19 12:35 -0700
  Re: Inserting stuff received with AJAX into the DOM bit-naughty@hotmail.com - 2017-08-19 12:55 -0700
    Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-20 12:16 +0200
      Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-20 15:55 +0200
        Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-20 19:18 +0200
          Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-20 21:50 +0200
            Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-20 22:39 +0200
              Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-21 08:29 +0200
                Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-21 16:44 +0200
                Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-21 17:24 +0200
                Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-21 17:47 +0200
                Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-21 19:50 +0200
                Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-21 22:16 +0200
                Re: Inserting stuff received with AJAX into the DOM Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-26 09:25 +0200
                Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-27 03:02 +0200
  Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-20 12:30 +0200
  Re: Inserting stuff received with AJAX into the DOM bit-naughty@hotmail.com - 2017-08-20 07:37 -0700
    Re: Inserting stuff received with AJAX into the DOM "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-20 17:17 +0200
    Re: Inserting stuff received with AJAX into the DOM Tim Streater <timstreater@greenbee.net> - 2017-08-20 17:48 +0100
  Re: Inserting stuff received with AJAX into the DOM bit-naughty@hotmail.com - 2017-08-20 11:21 -0700
    Re: Inserting stuff received with AJAX into the DOM Tim Streater <timstreater@greenbee.net> - 2017-08-20 19:29 +0100
    Re: Inserting stuff received with AJAX into the DOM "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-21 01:29 +0200
      Re: Inserting stuff received with AJAX into the DOM Andrew Poulos <ap_prog@hotmail.com> - 2017-08-21 16:29 +1000
        Re: Inserting stuff received with AJAX into the DOM "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-21 12:25 +0200
        Re: Inserting stuff received with AJAX into the DOM Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-21 16:47 +0200

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