typeof alternative

check.js

// typeof alternative

var check = function() {
  var args = Array.prototype.slice.call(arguments)
    , o = args[0]
    , a = args.slice(1)
  
  if (typeof o !== 'undefined' && (typeof o[a[0]] !== 'undefined') || !a.length && typeof o !== 'undefined')
    if (a.length > 1) { 
      b = o[a[0]]
      a.shift()
      a.unshift(b)
      return check.apply(this, a) 
    }
    else return true
  else return false
}

var x = { y: { z: 'foo' } }
  , u

console.log(check()) // false
console.log(check(x)) // true
console.log(check(x, 'y')) // true
console.log(check(x, 'y', 'z')) // true
console.log(check(x, 'y', 'z', 'k')) // false
console.log(check(u)) // false
console.log(check(u, 'a')) // false
console.log(check(x, 'a')) // false
console.log(check(x, 'y', 'a')) // false