I think they are learning tools for people to start and to play around. It is hard for an application developer with no background knowledge to understand what

I think they are learning tools for people to start and to play around. It is hard for an application developer with no background knowledge to understand what a parser does because it is quite abstract, for example lexer, tokens and expression tree. However, to build a realistic and comprehensive compiler, I believe to build it manually is a much better option because it is less error prone, more flexible to tweak around and favours unit testing. Perhaps parser generator is better? I am investigating these kind of tools for work because we need to make our own unique formula implementation. I did use yacc for a school project, and I know its limitation. Since I am busy at my staff so I just let my colleague to make their decision and they decide to use jison. It turns out the product owners want see a much better error message in invalidating the formula, also we need to define our own function so we have to switch to another implementation in the next phrase.