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Re: Get inner text of HMTL element

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Thomas 'PointedEars' Lahn wrote:
> Cezary Tomczyk wrote:
[...]
>>>> if (typeof document.getElementsByTagName('html')[0].textContent ===
>>>> 'string') {
>>>
>>> You should safely replace that with
>>>
>>>     if (typeof document.documentElement != "undefined"
>>>         && typeof document.documentElement.textContent == "string")
>>>     {
>>
>> or
>>
>> if (document.documentElement !== undefined && typeof
>> document.documentElement.textContent === 'string') {
>
> I wrote “safely” for a reason.  However,

Ok.

>    if (typeof document.documentElement != "undefined"
>        && document.documentElement !== null
>        && typeof document.documentElement.textContent == "string")
>    {
>
> should be even safer.
>
> Since this is a common task, it is useful to define a general method that
> takes an object reference and a list of property names as arguments, whereas
> the property names specify the “path” of a property such that the property’s
> value can be obtained by repeated property access along that list:
>
>    /**
>     * Determines if a value refers to an object.
>     *
>     * <p>Returns <code>true</code> if the value is a reference
>     * to an object; <code>false</code> otherwise.</p>
>     *
>     * <p>An value "is an object" if it is a function or
>     * <code>typeof "object"</code> but not <code>null</code>.
>     *
>     * @return {boolean}
>     */
>    function _isObject (a)
>    {
>      var t = typeof a;
>      return t == "function" || t == "object" && a !== null;

How about using toString() to get the type of object?

Object.prototype.toString.call(a).match(/\s([a-zA-Z]+)/)[1].toLowerCase()

>    }
>
>    return {
[...]
>      getFeature: function (obj) {
>        for (var i = 1, len = arguments.length; i < len; i++)
>        {
>          var arg = arguments[i];
>          if (_isObject(obj) && typeof obj[arg] != "undefined" && obj[arg])
>          {
>            obj = obj[arg];
>          }
>          else
>          {
>            return void 0;
>          }
>        }
>
>        return obj;
>      }
>    };
>
> See also: <http://PointedEars.de/wsvn/JSX/trunk/object.js>

Above idea looks good for me.

> A refined method would support specification of the property path as an
> Array of string values, and primitive false-values.  I am working on it.

That would be nice.

>>>>        get_inner_text = function(node) {
>>>>            return node.textContent;
>>>>        };
>>>> } else if (document.createTreeWalker) {
>>>
>>> Insufficient and error-prone feature test for a host object's method, see
>>> jsx.object.isHostMethod().
>>
>> Yes, I know isHostMethod, but still I am feeling that it's not enough.
>> Checking if host object is a function is one thing, but the second one
>> if it's native or not. Once I had a scenario where trim() method was
>> exists, but it was overwritten by some 3rd party library and this method
>> wasn't working well. I've just realized it after some investigation :-(
>>
>> However, last time I was thinking if it's strongly required every time
>> for every scenario. As I remember:
>>
>> 1. Some host objects in IE8 are as an "object", not a "function".
>> 2. There is type "unknown", but it's related to only one case.
>>
>> That's why I've been thinking that explicit conversion in that case is
>> relatively safe.
>
> Your logic is flawed.  It had been unrecoverable exceptions being thrown
> upon type-converting tests of host object's methods in MSHTML that prompted
> my/the creation of isMethod(), later isHostMethod(), in the first place.

You probably referring to 
http://robertnyman.com/2005/12/21/what-is-typeof-unknown/#comment-8001, 
right?

>>>>        get_inner_text = function(root) {
>>>>            var w = document.createTreeWalker(root, 4, null, false),
>>>>                result = '';
>>>>             while (w.nextNode()) {
>>>>                 result += w.currentNode.data;
>>>>             }
>>>>             return result;
>>>>        };
>>>>
>>>> } else {
>>>
>>> That the former two approaches fail does not mean that the third one must
>>> work.
>>
>> Hm, should I test if "firstChild" and "nextSibling" is supported before?
>> Or do something else?
>
> If you are to support “innerText” as well, *that* should be handled by the

I think I can skip innerText and support only textContent.

> last branch.  Anyhow, there is no guarantee that if some arbitrary element
> object has a “firstChild” or “nextSibling” property, the *target* element
> object also has it.
>
> Do you see now why it is a bad idea to infer from one property to another,
> even if the property names are the same and only the objects differ?

Then what options do I have?

1. Check, if firstChild and nextSibling is available on 
document.documentElement
or
2. Check, if every element support firstChild and nextSibling?

>>>>        get_inner_text = function(node) {
>>>>            var txt = '';
>>>>
>>>>            node = node.firstChild;
>>>>            while (node) {
>>>>                if (node.nodeType === 3 || node.nodeType === 4) {
>>>
>>> I avoid strict comparison against property values of host objects.  There
>>> are too many unknowns.
>>
>> I've never had problems with that, but I am not claim that there is no
>> problems. However, if you have a time then provide maybe some valuable
>> source where I can read about above problems. Otherwise, skip it, in
>> case of having no time.
>
> You are still operating in “Show me where it fails” mode in place of logic.

But "There are too many unknowns." doesn't teach me why.

>>>>                node = node.nextSibling;
>>>>            }
>>>>            return txt;
>>>>        };
>>>> }
>>>>
>>>> How about that?
>>>
>>> I do not think it is a good idea to infer from the existence of a
>>> property on one (host) object the existence of a property of the same
>>> name on another
>>
>> Hm, is it then better to do in that way?
>>
>> var get_inner_text = (function () {
>>
>>       // here check what is available and return function
>>
>> }());
>
> No, same problem: The feature test does not happen on the target object
> because that object is not reliably accessible yet (if it even exists).

So, the object itself must checked as well. It is in your above code, right?

>>> (host) object.  Therefore, I prefer approaches that test the properties
>>> of the target object instead.
>>
>> By "test" you mean using isHostMethod, isHostObjectProperty and
>> isRealObjectProperty?
>
> Yes, but not in the DM way, because that is error-prone even though it might
> be faster.

Ok, I will compare DM and your version.

>>> That aside, you should reconsider the actual probability that
>>> Node::textContent (DOM Level 3) would not be implemented but
>>> Document::createTreeWalker() (DOM Level 2 Traversal and Range) was.
>>
>> Hm, maybe it is worth it to remove textContent and focus only on
>> createTreeWalker or normal recursive iteration? Less code to maintenance.
>
> And much less efficient with regard to runtime and memory.  You should as
> yourself instead whether there is any actual *need* for tree-walking at this
> point.

Well, looking at 
https://developer.mozilla.org/en-US/docs/Web/API/Node.textContent looks 
like textContent is supported by major browsers. If I will drop IE8 
support then I can focus only on textContent, I think.

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

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Thread

Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-22 18:21 +0100
  Re: Get inner text of HMTL element Martin Honnen <mahotrash@yahoo.de> - 2014-02-22 19:31 +0100
    Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-22 20:51 +0100
      Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-22 21:11 +0100
        Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-22 21:37 +0100
          Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-22 22:05 +0100
            Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-22 23:38 +0100
              Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-23 10:43 +0100
                Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-23 14:50 +0100
                Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-23 15:48 +0100
                Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-24 21:01 +0100
                Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-24 22:34 +0100
                Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-27 21:41 +0100
                Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-27 22:32 +0100
                Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-28 13:44 +0100
                Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-28 16:54 +0100
                Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-03-04 20:51 +0100
                Re: Get inner text of HMTL element ompalompasales2@gmail.com - 2014-03-04 12:59 -0800
  Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-22 20:59 +0100
    Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-22 22:23 +0100
      Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-22 23:32 +0100
  Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-22 21:27 -0300
    Re: Get inner text of HMTL element "se" <se@no-one.here> - 2014-02-23 05:35 +0100
      Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-23 15:29 -0300
        Re: Get inner text of HMTL element "se" <se@no-one.here> - 2014-02-23 21:01 +0100
    Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-23 20:02 +0100
      Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-23 21:55 +0100
        Re: Get inner text of HMTL element Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2014-02-24 08:37 +0100
          Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-24 12:30 +0100
            Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-24 15:09 -0300
              Re: Get inner text of HMTL element Christoph Michael Becker <cmbecker69@arcor.de> - 2014-02-24 19:43 +0100
                Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-24 18:12 -0300
                Re: Get inner text of HMTL element Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-02-24 22:51 +0100
              Re: Get inner text of HMTL element Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-02-25 19:49 +0000
                Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-26 05:20 -0300
                Re: Get inner text of HMTL element "se" <se@no-one.here> - 2014-02-26 17:10 +0100
                OT - Re: Get inner text of HMTL element Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2014-02-26 15:48 -0300
                Re: OT - Re: Get inner text of HMTL element "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-02-26 22:43 +0100
                Re: OT - Re: Get inner text of HMTL element Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-02-27 15:00 +0000
                Re: OT - Re: Get inner text of HMTL element "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-02-28 10:50 +0100
                Re: OT - Re: Get inner text of HMTL element "se" <se@no-one.here> - 2014-02-27 10:57 +0100
                Re: Get inner text of HMTL element Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-02-27 15:46 +0000

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