สอบถามเรื่อง ชังค์ชั่น ที่ใช้สำหรับ ตรวจสอบขนาดของข้อความที่โพส ครับ

  <SCRIPT LANGUAGE="JavaScript"> 
// function parameters are: field - the string field, count - the field for remaining characters number and max - the maximum number of characters 
function CountLeft(field, count, max) { 
// if the length of the string in the input field is greater than the max value, trim it 
/*if (field.value.length >= max) 
field.value = field.value.substring(0, max); 
else 
// calculate the remaining characters 
*/
/*
if (field.value.length >= max)
	count.value = 0;
else
	count.value = max - field.value.length; 
	*/
	count.value = field.value.length;
} 
  </script> 
  </p>
  <p><font size="1" face="arial, helvetica, sans-serif">
    <textarea name="txtDescription" cols="30" rows="10" onKeyDown="CountLeft(this.form.txtDescription,this.form.left,50);" onKeyUp="CountLeft(this.form.txtDescription,this.form.left,50);" id="txtDescription"></textarea>
    <br>
    <input readonly type="text" name="left" size=10 maxlength=3 value="50">
    จำนวนตัวอักษร
  </font><br>
    <br>
</p>