我一直在使用浏览器聊天应用程序，除了能够向上滚动以查看窗口之外的先前消息之外，当我向上滚动滚动条突然跳到底部时，一切都很顺利的页面再次。
我试图通过从calc（100％ - 102px）更改.msg-are高度来解决这个问题。自动，然后页面加载到顶部，所有消息都在视图之外。
感谢任何帮助。
<html>
<head>
<title>Messenger</title>
<style type="text/css">
html {
height: 100%;
}
body {
margin: 0px;
padding: 0px;
height: 100%;
font-family: Helvetica, Arial, Sans-serif;
font-size: 14px;
}
.msg-container {
width: 100%;
height: 100%;
}
.header {
width: 100%;
height: 30px;
border-bottom: 1px solid #CCC;
text-align: center;
padding: 15px 0px 5px;
font-size: 20px;
font-weight: normal;
}
.msg-area {
height: calc(100% - 102px); /*This both fixes the scrolling problem but creates white space at the bottom of the page in doing so and hides messages */
width: 100%;
background-color:#F0F8FF;
overflow-y: scroll;
}
.msginput {
padding: 5px;
margin: 10px;
font-size: 14px;
width: calc(100% - 20px);
outline: none;
}
.bottom {
width: 100%;
height: 50px;
position: fixed;
bottom: 0px;
border-top: 1px solid #CCC;
background-color: #EBEBEB;
}
#whitebg {
width: 100%;
height: 100%;
background-color: #F0F8FF;
overflow-y: scroll;
opacity: 0.6;
display: none;
position: absolute;
top: 0px;
z-index: 1000;
}
#loginbox {
width: 600px;
height: 350px;
border: 1px solid #CCC;
background-color: #FFF;
position: fixed;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
z-index: 1001;
display: none;
}
h1 {
padding: 0px;
margin: 20px 0px 0px 0px;
text-align: center;
font-weight: normal;
}
button {
background-color: #43ACEC;
border: none;
color: #FFF;
font-size: 16px;
margin: 0px;
width: 150px;
}
.buttonp {
width: 150px;
margin: 0px auto;
}
.msg {
margin: 10px 10px;
background-color: #f1f0f0;
max-width: calc(45% - 20px);
color: #000;
padding: 10px;
font-size: 14px;
}
.msgfrom {
background-color: #0084ff;
color: #FFF;
margin: 10px 10px 10px 55%;
}
.msgarr {
width: 0;
height: 0;
border-left: 8px solid transparent;
border-right: 8px solid transparent;
border-bottom: 8px solid #f1f0f0;
transform: rotate(315deg);
margin: -12px 0px 0px 45px;
}
.msgarrfrom {
border-bottom: 8px solid #0084ff;
float: right;
margin-right: 45px;
}
.msgsentby {
color: #8C8C8C;
font-size: 12px;
margin: 4px 0px 0px 10px;
}
.msgsentbyfrom {
float: right;
margin-right: 12px;
}
</style>
</head>
<body onload="checkcookie(); update();">
<div id="whitebg"></div>
<div id="loginbox">
<h1>Pick a username:</h1>
<p><input type="text" name="pickusername" id="cusername" placeholder="Pick a username" class="msginput"></p>
<p class="buttonp"><button onclick="chooseusername()">Choose Username</button></p>
</div>
<div class="msg-container">
<div class="header">Messenger</div>
<div class="msg-area" id="msg-area"></div>
<div class="bottom"><input type="text" name="msginput" class="msginput" id="msginput" onkeydown="if (event.keyCode == 13) sendmsg()" value="" placeholder="Enter your message here ... (Press enter to send message)"></div>
</div>
<!--start JavaScript-->
<script type="text/javascript">
var msginput = document.getElementById("msginput");
var msgarea = document.getElementById("msg-area");
function chooseusername() {
var user = document.getElementById("cusername").value;
document.cookie="messengerUname=" + user
checkcookie()
}
function showlogin() {
document.getElementById("whitebg").style.display = "inline-block";
document.getElementById("loginbox").style.display = "inline-block";
}
function hideLogin() {
document.getElementById("whitebg").style.display = "none";
document.getElementById("loginbox").style.display = "none";
}
function checkcookie() {
if (document.cookie.indexOf("messengerUname") == -1) {
showlogin();
} else {
hideLogin();
}
}
function getcookie(cname) {
var name = cname + "=";
var ca = document.cookie.split(';');
for(var i=0; i<ca.length; i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1);
if (c.indexOf(name) == 0) return c.substring(name.length,c.length);
}
return "";
}
function escapehtml(text) {
return text
.replace(/&/g, "&")
.replace(/</g, "<")
.replace(/>/g, ">")
.replace(/"/g, """)
.replace(/'/g, "'");
}
function update() {
var xmlhttp=new XMLHttpRequest();
var username = getcookie("messengerUname");
var output = "";
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
var response = xmlhttp.responseText.split("\n")
var rl = response.length
var item = "";
for (var i = 0; i < rl; i++) {
item = response[i].split("\\")
if (item[1] != undefined) {
if (item[0] == username) {
output += "<div class=\"msgc\" style=\"margin-bottom: 30px;\"> <div class=\"msg msgfrom\">" + item[1] + "</div> <div class=\"msgarr msgarrfrom\"></div> <div class=\"msgsentby msgsentbyfrom\">Sent by " + item[0] + "</div> </div>";
} else {
output += "<div class=\"msgc\"> <div class=\"msg\">" + item[1] + "</div> <div class=\"msgarr\"></div> <div class=\"msgsentby\">Sent by " + item[0] + "</div> </div>";
}
}
}
msgarea.innerHTML = output;
msgarea.scrollTop = msgarea.scrollHeight;
}
}
xmlhttp.open("GET","get_messages.php?username=" + username,true);
xmlhttp.send();
}
function sendmsg() {
var message = msginput.value;
if (message != "") {
// alert(msgarea.innerHTML)
// alert(getcookie("messengerUname"))
var username = getcookie("messengerUname");
var xmlhttp=new XMLHttpRequest();
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState==4 && xmlhttp.status==200) {
message = escapehtml(message)
msgarea.innerHTML += "<div class=\"msgc\" style=\"margin-bottom: 30px;\"> <div class=\"msg msgfrom\">" + message + "</div> <div class=\"msgarr msgarrfrom\"></div> <div class=\"msgsentby msgsentbyfrom\">Sent by " + username + "</div> </div>";
msginput.value = "";
}
}
xmlhttp.open("GET","update_messages.php?username=" + username + "&message=" + message,true);
xmlhttp.send();
}
}
setInterval(function(){ update() }, 500);
</script>
</body>
</html>