I have two textarea and one of them has id attribute and other one doesn't has. Something like this:

<textarea> </textarea>
<textarea id = 'idname'> </textarea>

Now I need to select first textarea, How can I do that?

You could combine the :not() pseudo-class and the [id] attribute selector in order to negate elements with an id attribute:

textarea:not([id]) {}

document.querySelectorAll('textarea:not([id])');

$('textarea:not([id])');

Basic Example:

textarea:not([id]) {
  width: 100%;
}

<textarea></textarea>
<textarea id='idname'></textarea>

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