function wrap(fn) {

  // fast path if arity < 4, slow path if not

  switch (fn.length) {

    case 0:

      return function() {

        return fn.call(this)

      }

    case 1:

      return function() {

        return fn.call(this, this)

      }

    case 2:

      return function(a1) {

        return fn.call(this, this, a1)

      }

    case 3:

      return function(a1, a2) {

        return fn.call(this, this, a1, a2)

      }

    case 4:

      return function(a1, a2, a3) {

        return fn.call(this, this, a1, a2, a3)

      }

    default:

      return function() {

        const args = [this]

        for (let i = 0, len = arguments.length; i < len; i++) {

          args[i + 1] = arguments[i]

        }

        return fn.apply(this, args)

      }

  }

}

​

var f0 = wrap(function() { console.log(Date.now()) })

var f1 = wrap(function(a) { console.log(Date.now(), a) })

var f2 = wrap(function(a, b) { console.log(Date.now(), a, b) })

var f3 = wrap(function(a, b, c) { console.log(Date.now(), a, b, c) })

var f4 = wrap(function(a, b, c, d) { console.log(Date.now(), a, b, c, d) })

var f5 = wrap(function(a, b, c, d, e) { console.log(Date.now(), a, b, c, d, e) })