What is the most cheap way to mix `this` and other selectors in JQuery
<p>what is the best way to mix <code>this</code> with other selectors in JQuery  <code>:filter</code>,<code>[id=""]</code> and stuff like this, lets assume we wanna read <code>.val()</code> of an input with <code>name="input"</code> in form with that function is bind to it. </p>

<p>and if possible do they cost different ? if so why ?</p>

<p>here is the form </p>

<pre><code>&lt;form&gt;
&lt;input type="text" name="input"&gt;
&lt;/form&gt;
</code></pre>

<p>like we have this </p>

<pre><code>   $("form").submit(function(){

        if($(this).valid() == true){ //here  i wanna read the value of input with name test}
</code></pre>
