How JavaScript is used in Blockchain & Cryptocurrencies?

Could you elaborate on how JavaScript finds its way into the intricate world of blockchain and cryptocurrencies? I'm curious to understand how this widely-used programming language contributes to the development and operation of decentralized systems. What specific aspects of blockchain do JavaScript developers focus on? Are there any specific frameworks or libraries that are preferred for building blockchain applications? Furthermore, how does JavaScript handle the security requirements that are paramount in the cryptocurrency space? And lastly, what are some of the challenges and limitations that JavaScript developers encounter when working with blockchain technology?