Awfully silly interfaces

gistfile1.js

var interface = function(inter){
  return {
    test: function(testee) {
      for ( var prop in inter ) {
        if ( !(prop in testee) ) return false }
      return true
    }
  }
}

var myInter = interface({ x: true, y: true, f: true })
  , result1 = myInter.test({ x: 45, y: 23, f: null }) // true
  , result2 = myInter.test({ x: 45, y: 23, f: undefined, foo: 'sd' }) // true
  , result3 = myInter.test({ x: 45, y: 45 /* missing f */ }) // false

console.log(result1, result2, result3)