why there are different kinds of js libraries like node js, angular js, react js etc.

Question

why there are different kinds of js libraries like node js, angular js, react js etc.

Answer 1

To reduce size, complexity,load time of a website or webpage used for different porpose

Answer 2

They are not libraries. Node.js is a runtime environment. The rest are frameworks. Each one of them has different implementations and purposes. You can read more about their differences here https://en.m.wikipedia.org/wiki/Comparison_of_JavaScript_frameworks
Edit: if you want to know what a framework is in the first place, read this: https://skillcrush.com/blog/what-is-a-javascript-framework/#whatis