Your javaScript code executed in V8(Chrome) or SpiderMonkey(FireFox) engine in the browser

The engine parse your code and compile it into machine code and then it excecutes that machine code then you see the webpage

javaScript is a dynamic, interpreted and weakly typed progamming language

Dynamic, interpreted means that it's not pre-compiled like other language as like c++, other language get compiled during or after development but javaScript get compiled and evaluated at runtime and it's called fly compiled, it also means that the code can change at runtime