The Lambda Calculus, or λ-calculus, is probably the most basic programming language constructed. It consists of anonymous functions that can either be constructed, abstractions, or applied, reduced. Nothing more. These two in composite actually makes up for a turing complete programming language. You apparently do not need more features to program.
Though advanced programming is quite cumbersome using the Lambda Calculus, in academics this language has its usages - in model theory it can be used as a turing complete base case instead of a turing machine. And it isn't that hard to construct. So let's build the λ-calculus in java script.
You can skip the project and just use the application by clicking here. Or you can jump directly to the git repo by clicking here.