how to check if a key exists in an object javascript

myObj.hasOwnProperty('key') // it checks object for particular key and not on prototype   if (obj.hasOwnProperty("key1")) {
  ...
}!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"
"key" in obj // true, regardless of the actual value