Javascript encoding

Very handy when you have PHP writing out Javascript code that could contain user-entered data (like carriage returns). It will look ugly in the source view, but it works great.

   // see http://www.the-art-of-web.com/javascript/escape/
    function js_encode($str) {
      $new_str = '';;

       for($i = 0; $i < strlen($str); $i++) {
          $val = ord(substr($str, $i, 1));
          $prefix = $val < 16 ? '\\x0' : '\\x';
          $new_str .= $prefix . dechex($val);
       }

       return $new_str;
    }

Overriding an event handler programmatically

Say you already have this somewhere, and want an onsubmit() handler, and can't change it...

<FORM method="POST" id="the_form" name="the_form" enctype="multipart/form-data" action="<?= $url ?>">

You can do this:

el = document.getElementById("the_form");
el.onsubmit=function() { return check_submit(this);}

Trick: checkboxes in JS and HTML

Thanks to IndyBob here

To make multiple checkboxes appear in the POST results, you must declare them in this array notation:

<INPUT TYPE="CHECKBOX" name="choice[]" value="<?=$k?>"><?=$c->radio_tag?></INPUT>

To read these in JS, do this:

   // check to see if any are picked
   for (var i = 0; i < document.the_form.elements['choice[]'].length; i++)
   {  if (document.the_form.elements['choice[]'][i].checked)
      {  picked = true;
         break;
      }
   }  

-- MattWalsh - 14 Sep 2009