javascript - When clicked on bold or italic tag cursor to be in middle? -

i'm using code in 1 of torrent websites. when click on 'b' tag next code shows [b][/b]. however, when done cursor's position @ beginning of these tags instead of in middle, this: [b]cursor here[/b]

this code:

<script type="text/javascript"> function bbtag(tag, s, text, form) {     switch (tag) {         case '[url]':             var start = document.forms[form].elements[text].selectionstart;             var end = document.forms[form].elements[text].selectionend;             if (start != end) {                 var body = document.forms[form].elements[text].value;                 var left = body.substr(body, start);                 var middle = "[url]" + body.substring(start, end) + "[/url]";                 var right = body.substr(end, body.length);                 document.forms[form].elements[text].value = left + middle + right;             } else {                 document.forms[form].elements[text].value = document.forms[form].elements[text].value + "[url][/url]";             }             document.forms[form].elements[text].focus();     } 

this code inserting these tags:

<td align="center">     <input type="button" name="url" value="url " onclick="javascript: bbtag('[url]', 'url', '<?php echo $name; ?>', '<?php echo $form; ?>')" /> </td> 

you forgot close function curly bracket:

<script type="text/javascript">     function bbtag(tag, s, text, form) {         switch (tag) {             case '[url]':                 var start = document.forms[form].elements[text].selectionstart;                 var end = document.forms[form].elements[text].selectionend;                 if (start != end) {                     var body = document.forms[form].elements[text].value;                     var left = body.substr(body, start);                     var middle = "[url]" + body.substring(start, end) + "[/url]";                     var right = body.substr(end, body.length);                     document.forms[form].elements[text].value = left + middle + right;                 } else {                     document.forms[form].elements[text].value = document.forms[form].elements[text].value + "[url][/url]";                 }                 document.forms[form].elements[text].focus();         }     // miss function closing curly bracket here </script> 

i advise work clean indented code. next time spot these kind of errors.