运动四 ---- 训练逻辑思维第四步

function getStyle(obj,attr){
return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj,1)[attr];
}

function sport_03(obj,attr,target){
clearInterval(obj.timer);
obj.timer = setInterval(()=>{
let cur = parseInt(parseFloat(getStyle(obj,attr)) * 100);
let speed = (target - cur) / 8; //基数
speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);
if(cur === target){
clearInterval(obj.timer);
}else{
obj.style.opacity = (cur + speed) / 100;
obj.style.filter = ‘alpha(opacity’ + (cur + speed) +’)’;
}
},30)
}