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From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: Multiple inputs with same event
Date: Wed, 10 Jun 2020 17:12:25 +0200
Organization: PointedEars Software (PES)
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Andrew Poulos wrote:

> On 9/06/2020 10:49 am, Thomas 'PointedEars' Lahn wrote:
>> It is actually not necessary (but recommended by some people) do this
>> with assignment with scripting.  However, a form element can have an
>> “onchange” event-handler attribute that can execute code, like a
>> function:
>> 
>>    <form … onchange='my.change(this, event)'>
>>      …
>>    </form>
>> 
>> Then the form element does not need an “id” attribute, and the reference
>> to object representing the current propagated event and to the object
>> representing the form element, can be obtained by passing the “event” and
>> “this” values respectively.
>> 
>> Note that the “change” event might not be fired for every control.
> 
> For the few times that an input is changed with code, and so doesn't
> trigger an "on change" event, I'm going to trigger the change with
> 
> document.querySelector('form').dispatchEvent(new Event('change'));

  document.forms[0].dispatchEvent(new Event('change'));
  ^^^^^^^^^^^^^^^^^
suffices as for the first reference, and is more efficient and compatible. 

Your “change” event might need an event target to be useful; then just 
passing the constructor return value might not be sufficient.

Note that for compatibility you may need an “Event” wrapper, like the 
following quickhack:
 
  var _isHostMethod = jsx.object.isHostMethod; // [1]
  var e = null;

  if (typeof Event == 'function')
  {
    try
    {
      e = new Event('change');
    }
    catch (e)
    {
      if (!(e instanceof TypeError)) throw e;
    }
  } 

  if ((!e || e.type != 'change') && _isHostMethod(document, 'createEvent'))
  {
    try
    {
      e = document.createEvent('Event');
      if (_isHostMethod(e, 'initEvent')) e.initEvent('change', true, true);
    }
    catch (e)
    {
      if (_isHostMethod(_global, 'console', 'log')) console.log(e);
    }
  }

<https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events>

[1] <https://github.com/PointedEars/JSX/blob/master/object.js#L1051>

(Maybe I find the time to write a general wrapper during the summer 
holidays, and update JSX.)
 
> Is it appropriate as the value of "this" won't change?

In theory, yes.  It depends on what you want to do.

-- 
PointedEars
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