兼容主流浏览器的js原生函数封装

1.获取和修改垂直滚动条的滚动距离

    
//获取滚动条滚动距离
function getScrollTop(){
        var    fromTop=document.documentElement.scrollTop||document.body.scrollTop||window.pageYOffset;
        return fromTop;
    }
//修改滚动条滚动距离
function changeScroll(num){
        if(document.documentElement.scrollTop){
            document.documentElement.scrollTop+=num;
        }
        else if(document.body.scrollTop){
            document.body.scrollTop+=num;
        }
        else{
            window.pageYOffset+=num;
        }
    }

2.倒计时函数，需要创建一个id为countdown的div；

function countDown(time){      ///time为倒计时的秒
                var timer;
                var hours,minutes,seconds;
                timer=setInterval(function(){
                    if(time==0){
                        clearInterval(timer);
                    }
                    console.log();
                    hours=parseInt((time/60)/60);
                    minutes=parseInt((time/60)%60);
                    seconds=parseInt(time%60);
                    hours=hours>9?hours:"0"+hours;
                    minutes=minutes>9?minutes:"0"+minutes;
                    seconds=seconds>9?seconds:"0"+seconds;
                    document.getElementById("countdown").innerHTML=hours+":"+minutes+":"+seconds;
                    time--;
                },1000);
            }

持续更新中......