How to add a placeholder attribute if "value" field is empty
<p>Is there a way to add a placeholder attribute (placeholder tag, not "defaultvalue" and similar approaches) if you have an text input field that has "value" property empty?</p>

<p>I have seen many similar questions here, but most of them use defaultvalue. I need placeholder tags and additionally I can't influence HTML output at all.</p>

<p>This is the given HTML output example:</p>

<pre><code>&lt;input type="text" value="" name="textbox" id="edit-textbox"&gt;
</code></pre>
