I don't see what is challenging about any of what you mentioned, furthermore parsing a language is not the same thing as verifying that what is parsed is a sema

I don't see what is challenging about any of what you mentioned, furthermore parsing a language is not the same thing as verifying that what is parsed is a semantically valid. Python is almost a context free language with the exception of how it handles indentation. With indentation taken into account, the entire language can be parsed directly from the following grammar using something like yacc: https://docs.python.org/3/reference/grammar.html https://docs.python.org/3/reference/grammar.html JavaScript is not a strictly context free grammar either, but like Python the vast majority of it is and the parts that are not context free can be worked around. Furthermore the entire grammar is available here: https://262.ecma-international.org/5.1/#sec-A https://262.ecma-international.org/5.1/#sec-A It isn't trivial to work around the parts that aren't context free, but it's also nothing insurmountable that requires more than 120 hours of effort. The document explicitly points out which grammar rules are not context free and gives an algorithm that can be used as an alternative. Parsing is really not as challenging a job as a lot of people make it out to be and it's an interesting exercise to try yourself and get an intuitive feel for. You can use a compiler compiler (like yacc) if you feel like it to just get something up and running, but the downside of such tools is they do very poorly with error handling. Rolling out a hand written parser gives much better error messages and really is nothing that crazy. C++ is the only mainstream language I can think of that has a grammar so unbelievably complex that it would require a team of people working years to implement properly (and in fact none of the major compilers implement a proper C++ parser). For statically typed languages things get harder because you first need to parse an AST, and then perform semantic analysis on it, but if all you need is syntax highlighting, you can skip over the semantic analysis.