function animate(obj, target) {        clearInterval(obj.timer);        obj.timer = setInterval(function () {            var leader = obj.offsetLeft;            var step = 10;//之前只能是正数 只能往右走            /*if (leader < target) {             step = step;             } else {             step = -step;             }*/            step = leader < target ? step : -step;            //if (leader != target) {            //Math.abs(target - leader) 当前位置到目标的距离            //当前位置到目标的距离如果很大 这一步迈出之后 到不了目标 或者正好到            // 就可以迈出这一步            if (Math.abs(target - leader) >= Math.abs(step)) {                leader = leader + step;                obj.style.left = leader + "px";            } else {                //就差一点儿了手动放到目标即可                obj.style.left = target + "px";                clearInterval(obj.timer);            }        }, 15);    }