1.设置为空白图像
document.getElementById('dynamicImage').src = 'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7';
2. 或者设置为透明图像
document.getElementById('dynamicImage').src = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGtvHsMAAAAASUVORK5CYII=';