JavaScript is a High-level, single-threaded, JIT-compiled, Garbage collected, prototype-based, multi-paradigm, dynamic language with a non-blocking event loop also with functions as first class citizens.

JavaScript is signle threaded Non Blocking programming language with an event loop in it.

this means it can execute only one signle piece

1const parent = () => {
2  const child = () => {
3    console.trace();
4  }
5  child();
6}
7
8parent();