js获取窗口滚动条高度、窗口可视范围高度、文档实际内容高度、滚动条离浏览器底部的高度

//获取窗口可视范围的高度
function getClientHeight(){  
    var clientHeight=0;  
    if(document.body.clientHeight&&document.documentElement.clientHeight){  
        var clientHeight=(document.body.clientHeight<document.documentElement.clientHeight)?document.body.clientHeight:document.documentElement.clientHeight;
    }else{  
        var clientHeight=(document.body.clientHeight>document.documentElement.clientHeight)?document.body.clientHeight:document.documentElement.clientHeight;
    }  
    return clientHeight;  
}function getC