jquery实现表单验证并阻止非法提交

<script type="text/javascript">//jQuery代码function confirm(){　　if($("#advice").val().length == 0){　　alert("We can't see your advice. Maybe you should fill the form first.");　　$("#advice").focus();　　return false;}else if($("#advice").val().length <= 15){　　alert("Your advice should longer than 15 letters.");　　$("#advice").focus();　　return false;}else{　　alert("Thank you for your advice! You will get out reply in 24 hours for advice:/n"+$("#advice").val());　　return true;}}</script><form action="" method="post" onSubmit="return confirm();" >　　<textarea id="advice" rows="20" cols="50"placeholder="Give us some advice?"></textarea>　　 <input type="submit"value="Thank you"/></form>