效果：
代码：
html：
<div id="box">
<div id="left"></div>
<div id="resize"></div>
<div id="right"></div>
</div>
css：
body,html{
margin:0;
padding:0;
height:100%;
}
#box{
width:600px;
height:500px;
overflow:hidden;
}
#left{
width:calc(30% - 5px);
height:100%;
background:skyblue;
float:left;
}
#resize{
width:5px;
height:100%;
cursor: w-resize;
float:left;
}
#right{
float:right;
width:70%;
height:100%;
background:tomato;
}
javascript：
window.onload = function(){
var resize = document.getElementById("resize");
var left = document.getElementById("left");
var right = document.getElementById("right");
var box = document.getElementById("box");
resize.onmousedown = function(e){
var startX = e.clientX;
resize.left = resize.offsetLeft;
document.onmousemove = function(e){
var endX = e.clientX;
var moveLen = resize.left + (endX - startX);
var maxT = box.clientWidth - resize.offsetWidth;
if(moveLen<150) moveLen = 150;
if(moveLen>maxT-150) moveLen = maxT-150;
resize.style.left = moveLen;
left.style.width = moveLen + "px";
right.style.width = (box.clientWidth - moveLen - 5) + "px";
}
document.onmouseup = function(evt){
document.onmousemove = null;
document.onmouseup = null;
resize.releaseCapture && resize.releaseCapture();
}
resize.setCapture && resize.setCapture();
return false;
}
}
