It's similar to the metacircular Scheme interpreter in Scheme in SICP. It's not that interpreting JavaScript in JavaScript (especially if that JavaScript is run

It's similar to the metacircular Scheme interpreter in Scheme in SICP. It's not that interpreting JavaScript in JavaScript (especially if that JavaScript is running on a full-blown and more efficient interpreter itself) is a practical end, but that it demonstrates a concept: language as data and data as language. As an implementation, it is merely interesting -- but imagine writing code in a language closer to the problem domain you're working with that just happens to run on JavaScript.