JavaScript blank validation or no solution

JavaScript blank verification or not
This is a restaurant website, the menu can select the number of dishes, and then put in the shopping cart inside.

PHP Code

  
  while (...) {echo "";}

Before the Post asked, but I asked the wrong, form is in the loop inside, so can not use getElementById to judge. Thank you for T5500 help me here.
There is only one input type=text in each form. Now, before each form is submitted, how can you tell that each text cannot be empty or 0?


------Solution--------------------
Onsubmit= ' return dosubmit (); '
Switch
Onsubmit= ' return dosubmit (this); '

Js

JScript Code

function Dosubmit (FMT) {  if (Fmt.textbox_qty.value = = ") {    fmt.textbox_qty.focus ();    Alert (' cannot be null ');    return false;  }  return true;}
------Solution--------------------
function IsEmpty ()
{
   function IsEmpty () {
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