Function to partially apply function args even if the function might be "manually curried".

papply.js

export const papply =
    (f, ...x) => {
        const arity = f.length
        const args = x.length
        
        // shortcut no-ops for perf
        if (args === arity) return f(...x)
        if (args === 0) return f
      
        if (args < arity) {
          return (...y) => papply(f, ...x.concat(y))
        }
        else {
            const g = f(...x.slice(0, arity))
            return papply(g, ...x.slice(arity))
        }
    }

/*
> papply((a, b) => (c) => a + b + c, 1, 2, 3)
6
> papply((a, b) => (c) => a + b + c, 1, 2)(3)
6
> papply((a, b) => (c) => a + b + c, 1)(2, 3)
6
> papply((a, b) => (c) => a + b + c, 1)(2)(3)
6
*/