效果图如下：
代码如下：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
body {
100%;
height: 100%;
}
* {
margin: 0 auto;
padding: 0;
}
#bgimg1 {
background-size:100% 100%;
position: relative;
text-align: center;
background-image: url(../img/iphone.png) ;
404px;
height: 800px;
}
#bgcolor1 {
overflow-y:auto;
overflow-x: hidden;
position: absolute;
text-align: left;
left: 45px;
top: 125px;
305px;
}
#bgcolor2 {
left: 47px;
top: 640px;
310px;
height: 40px;
position: absolute;
}
#text1 {
margin-left: 25px;
border: none;
border-radius: 5px;
height: 30px;
220px;
}
#btn1 {
border: none;
border-radius: 4px;
30px;
height: 30px;
background: #f0f0f0;
}
#change1 {
position: absolute;
float: left;
background: #FFF;
border: thin 1px;
left: 4px;
30px;
height: 30px;
border-radius: 5px;
}
#btn1:hover {
cursor: pointer;
}
/*#bgcolor2 img{
left:-2px;
position:absolute;
background:#FFF;
border:thin 1px;
border-radius:4px;
30px;
height:28px;*/
#change1:hover {
cursor: pointer;
}
#ul1 {
list-style-type: none;
}
.sp01 {
color: #fff;
padding-left: 5px;
padding-right: 5px;
margin-left: 30px;
word-break: break-all;
/*注意：如果不添加强制换行，中文可以自动换行，英文则不能自动换行*/
display: inline-block;
line-height: 28px;
border: 1px thin;
border-radius: 5px;
background: #9C3;
}
.sp02 {
color: #FFFF99;
padding-left: 5px;
padding-right: 5px;
margin-right: 30px;
word-break: break-all;
/*注意：如果不添加强制换行，中文可以自动换行，英文则不能自动换行*/
display: inline-block;
line-height: 28px;
border: 1px thin;
border-radius: 5px;
color: #9c3;
background: yellow;
float: right;
}
.pic01 {
265px;
background: url(../img/1.jpg) no-repeat left top;
float: left;
margin-top: 10px;
margin-left: 10px;
}
/*注意：不设置div的高度，这样div的高度会随着内容变化，由内容撑起高度*/
.pic02 {
265px;
background: url(../img/2.jpg) no-repeat right top;
float: right;
margin-top: 10px;
margin-right: 10px;
}
</style>
</head>
<body>
<div id="bgimg1">
<div id="bgcolor1">
<!--这个div是用来放js生成的内容的-->
</div>
<div id="bgcolor2">
<img id="change1" src="../img/1.jpg">
<input type="text" value="" id="text1">
<input type="button" value="发送" id="btn1">
</div>
</div>
<script>
window.onload = function() {
var oForm = document.getElementById("form1");
var oText = document.getElementById("text1");
var oBtn = document.getElementById("btn1");
var oChange = document.getElementById("change1");
var oContent = document.getElementById("bgcolor1");
var oUl = document.getElementById("ul1");
var onOff = true;
//var oSet=oContent.offsetHeight;/*获取元素高度。注意：如果样式不是写在行内的，是不能直接通过style.width获得元素高度的*/
oChange.onclick = myFunction; /*切换聊天图片*/
function myFunction() {
if(onOff) {
oChange.src = '../img/2.jpg';
onOff = false;
} else {
oChange.src = '../img/1.jpg';
onOff = true;
}
}
oBtn.onclick = function() {
if(oText.value == '') {
alert('请输入点内容吧~ ~');
} //注意：alert()的括号中，字符串要加引号才行
else {
if(onOff) {
oContent.innerHTML += '<div class="pic01">' + '<span class="sp01">' + oText.value + '</span>' + '</div>';
} else {
oContent.innerHTML += '<div class="pic02">' + '<span class="sp02">' + oText.value + '</span>' + '</div>';
};
oText.value = '';
}
};
/* if(oSet==0){oContent.style.overflowY='scroll'};*/
}
</script>
</body>
</html>
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