移动函数的封装示例

function doMove ( obj, attr, dir, target, endFn ) {
    
    dir = parseInt(getStyle( obj, attr )) < target ? dir : -dir;
    
    clearInterval( obj.timer );
    
    obj.timer = setInterval(function () {
        
        var speed = parseInt(getStyle( obj, attr )) + dir;            // 步长
        
        if ( speed > target && dir > 0 ||  speed < target && dir < 0  ) {
            speed = target;
        }
        
        obj.style[attr] = speed + 'px';
        
        if ( speed == target ) {
            clearInterval( obj.timer );
            
            /*
            if ( endFn ) {
                endFn();
            }
            */
            endFn && endFn();
            
        }
        
    }, 30);
}

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