I started to learn shader programing for WebGL, but I am facing issues while learning it

I started to learn it from the book of shaders, but there are lots of concepts I am not getting it like: What is inside u_resolution and why the sometimes they are using maths functions. I forgot lots of math, I also need to learn necessary maths for it

Maybe simple examples will help you?

From the Collection of examples from discourse.threejs.org

see Little Shader Book

This resource is good for pure shader development but not for WebGL in general. Beginners should start with a respective WebGL book (just google the topic). For three.js specific resources, have a look at the Resources section at the homepage.

thank you so much for your reply.
I checked the Resources section but didn’t find any specific section for shaders.
I don’t want to learn WebGL, I learn three.js and want to use shaders inside it.
can you please suggest me resource to learn shader programming?(I am trying to learn it from 3 days).
I searched for webGL but didn’t found good resources.

thanks for your reply, I’ll check it