class Utils {

//获取中间任意个数的定位元素到body的offsetLef距离
    static getOffset(obj){
        let o={left:obj.offsetLeft,top:obj.offsetTop};
        while(obj.offsetParent){
            obj=obj.offsetParent;
            o.left+=obj.offsetLeft
            o.top+=obj.offsetTop;

            return o;
        }
    }

//获取元素样式
    static getStyle(obj, attr) {
        if (obj.currentStyle) {
              //兼容写法 IE8以及以下版本
            return obj.currentStyle[attr]

        }
        return window.getComputedStyle(obj, null)[attr];
    }
      //获取不可见区域高度
    static getScroll() {
        if (window.pageXOffset != undefined) {
            return {
                left: window.pageXOffset,
                top: window.pageYOffset
            }
        } else if (window.compatMode == "CSS1Compat") {
            return {
                left: document.documentElement.scrollLeft,
                top: document.documentElement.scrollTop
            }
        }
        return {
            left: document.body.scrollLeft,
            top: document.body.scrollTop
        }
    }
    
//缓冲动画库
    static animate(oEle, json, callback) {
        // 1.清空定时器
        clearInterval(oEle.timer);
        // 2.开启定时器
        oEle.timer = setInterval(() => {
            let flag = true;
            // 开启遍历
            for (let attr in json) {
                let target = 0;
                let current = 0;

                if (Object.is(attr, "opacity")) {
                    target = parseFloat(json[attr]) * 100;
                    current = parseFloat(Utils.getStyle(oEle, attr)) * 100;
                } else {
                    target = parseInt(json[attr]);
                    current = parseInt(Utils.getStyle(oEle, attr));
                }

                //步长=(目标值-当前值)/10;
                let steps = (target - current) / 10;
                steps = steps >= 0 ? Math.ceil(steps) : Math.floor(steps);

                // 新的位置 = 当前值+ 步长
                if (attr == "opacity") {
                    oEle.style[attr] = (current + steps) / 100;
                } else if (attr == "zIndex") {
                    oEle.style[attr] = target;
                } else {
                    oEle.style[attr] = (current + steps) + "px";
                }

                if (current != target) {
                    flag = false;
                }
            }

            if (flag) {
                clearInterval(oEle.timer)
                if (typeof (callback) == "function") {
                    callback();
                }
            }
        }, 15)
    }
}