Almost all modern programming languages have parsers for that language either as a standard library feature or as a package available in the ecosystem. That means it's very easy to run a production quality parser over an input string and then validate and the interpret the resultant AST as you see fit.

Besides that approach, simply rolling your own parser using a parser combinator library is super simple. The word combinator makes it seem complicated, but it's actually the opposite, using parser combinators is a lot simpler than writing a parser the traditional way you might have learned in formal education.

Implementing a simple DSL like for example an event-filtering language should cost a competent but fully inexperienced programmer maybe 1 or 2 weeks for a proof of concept, and then 3-6 more weeks to get it production ready depending on the feature set of course.

Of course, that's more time than simply running the V8 interpreter over your input string, and maybe running the V8 interpreter over your input string is an awesome way to empower your (trusted) customers.