How can I figure out whether mipmaps were generated? (three.js)

Question

How can I figure out whether mipmaps were generated for my textures? The "mipmaps" property of the texture is just for manual mipmapping and is empty per default, right?

My textures are power of 2, and that's what I do with them:

texture.minFilter = THREE.LinearMipMapLinearFilter;
texture.magFilter = THREE.LinearFilter;
texture.needsUpdate = true;

Thanks for a hint!