JS：图片等比例缩放

// 等比例缩放
var bili = 1;
if (imgWidth > imgHeight && imgWidth > 400) {
bili = imgWidth / 400;
 imgWidth = 400;
imgHeight = imgHeight / bili;
} else if (imgWidth < imgHeight && imgHeight > 300) {
 bili = imgHeight / 300;
imgHeight = 300;
imgWidth = imgWidth / bili;
 }