小程序开发怎样可以判断JSON里面有没有某个KEY

[图片] [图片]有办法吗？

小程序有没有办法可以做到全局广播

求base64的数据转成图片的方法

小程序中有没有eval()的替代方案？

[图片]就这样两行代码就报错了， [图片] [图片]这是后台接口返回的base64位的数据，既res.data.img的数据 "/9j/4AAQSkZJRgABAgAAAQABAAD/2wBDAAgGBgcGBQgHBwcJCQgKDBQNDAsLDBkSEw8UHRofHh0a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"