（用戶名的class為a,密碼的class為b,確認密碼的class為c）?<script type="text/javascript">?function?check(){ ????var?yonghu=document.getElementById("a"); ????var?pwone=document.getElementById("b");?var pwtwo=document.getElementById("c"); ????if(yonghu.value?==?""?||?b.value?==?"") { ????alert("用戶名或密碼不能為空"); ????}?if(b.value!=c.value) {?alert("密碼與確認密碼不一致"); }?}</script>?..........?<input class="tijiao" type="submit" value="提交" onclick="check()" />