Not to mention the fact that the landscape of GLSL compilers is fairly broad and you have absolutely no control over whether or not you have one worth anything (frequently on mobile, you don't).
Unfortunately, the fact that shader code is hard to write, and has a huge number of performance pitfalls mean that you're going to have to inspect the source of any non-trivial library you use, and in most cases you'll probably need to write it yourself, if you care.
Here, I took the time to look at a few from NPM.
- https://github.com/Jam3/glsl-hsl2rgb/blob/master/index.glsl This is awful. Data dependant branching absolutely destroys performance on the GPU. A vectorized, zero branch solution to this exists and is fairly well known, the author just doesn't know it or doesn't care. - https://github.com/hughsk/glsl-dither/blob/master/2x2.glsl A neat effect, but the statement above is still true. The other dimensions (4x4 and 8x8) are even worse.
There are others as well. The point seems to be that many of them that are doing something other more complicated than a couple lines, are not well written for code that runs on the GPU and are going to perform very poorly in practice.