What is the most cheap way to mix `this` and other selectors in JQuery

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

and if possible do they cost different ? if so why ?

here is the form

<form>
<input type="text" name="input">
</form>

like we have this

   $("form").submit(function(){

        if($(this).valid() == true){ //here  i wanna read the value of inp开发者_如何学运维ut with name test}

The selector would just be:

var myVal = $("#test input[name=input]").val();

The this version would use .find() like this:

var myVal = $(this).find("input[name=input]").val();

...which is faster depends on the browser and what it supports, namely if it supports querying by selectors relatively.

use find maybe?