这个是我搜索页面，如果输入框内无文字，则弹出提示。
如果多项输入框都没有问题，则弹出框一并提示。
function isvaild()
{ var messagea = "";
var messageb = "";
var messagec = "";
var messaged = "";
var messagee = "";
var messagef = "";
var messageg = "";
var messageh = "";
var messagei = "";
var messagej = "";
var messagek = "";
var messagel = "";
var messagem = "";
var a = document.getElementByName("classno").value;
var b = document.getElementByName("classalltime").value;
var c = document.getElementByName("classname").value;
var d = document.getElementByName("classexpe").value;
var e = document.getElementByName("selectscore").value;
var f = document.getElementByName("classroom").value;
var g = document.getElementByName("teaname").value;
var h = document.getElementByName("teano").value;
var i = document.getElementByName("dateStr").value;
var j = document.getElementByName("classbook").value;
var k = document.getElementByName("classtime").value;
var l = document.getElementByName("note").value;
var m = document.getElementByName("stunumber").value;
