basic arithmetic memoization - failed try

foo.js

const app = require('parse-function')()

let cacheHits = 0
const cache = {}

function memoizeArithmetic(arithmeticExpr) {
  function __memoizedArithmeticFn__() {
    // not too efficient! probably `split` could be used..
    const key = app
      .parse(arithmeticExpr)
      .body.trim()
      .replace(/\s/, '')

    if (cache.hasOwnProperty(key)) {
      console.log('hits', (cacheHits = cacheHits + 1))
      return cache[key]
    }
    console.log('cached!')
    return (cache[key] = arithmeticExpr())
  }
  __memoizedArithmeticFn__.__proto__.__isArithmeticExpression = true

  return __memoizedArithmeticFn__
}

// const basic = memoizeArithmetic(() => (1 + 2) / 6)
// const basic2 = () => (1 + 2) / 6

// console.log(basic.__isArithmeticExpression)
// console.log(basic2.__isArithmeticExpression)

let i = 0
Function.prototype.call = new Proxy(Function.prototype.call, {
  apply: (targetFn, ctx, args) => {
    if (targetFn.__isArithmeticExpression) {
      return targetFn
    }
    return Reflect.apply(targetFn, ctx, args)
  },
})

const foo = memoizeArithmetic((a, b) => `${a} hi ${b}`)

// console.log(i)
console.log(foo.call())