JavaScript is an integral part of any website. It is responsible for all its logic and data manipulation. It is the most popular language used to build websites. This extremely versatile language can be used for virtually anything. This does not necessarily mean that it will best suit all applications, but it will be able to compete with the leading languages in many respects. It is this versatility that makes it worth finding out about its underlying mechanisms and thus its strengths and drawbacks. 

JavaScript is single-threaded, which means that only one action can be performed at a time. JavaScript uses a single thread to handle all requests, but when creating contexts, it uses other threads to handle input/output, so it does not get stuck. JavaScript can communicate between threads, using external interfaces that are able to create such other threads, it can communicate. For example, if you create a web page, it runs on a single thread but is able to communicate with other threads that work for some specific purpose. This is the case when using a camera. The camera is such a separate service for the browser and is a separate thread. And this is not happening on our thread but on an external one.