hasOwnProperty()
method and the other uses the in
keyword. If we have an object users
with a property of Alan
, we could check for its presence in either of the following ways:
users.hasOwnProperty('Alan');
'Alan' in users;
// both return true
users
, with some users in it and a function isEveryoneHere
, which we pass the users
object to as an argument. Finish writing this function so that it returns true
only if the users
object contains all four names, Alan
, Jeff
, Sarah
, and Ryan
, as keys, and false
otherwise.
users
object only contains the keys Alan
, Jeff
, Sarah
, and Ryan
'
testString: 'assert("Alan" in users && "Jeff" in users && "Sarah" in users && "Ryan" in users && Object.keys(users).length === 4, "The users
object only contains the keys Alan
, Jeff
, Sarah
, and Ryan
");'
- text: 'The function isEveryoneHere
returns true
if Alan
, Jeff
, Sarah
, and Ryan
are properties on the users
object'
testString: 'assert(isEveryoneHere(users) === true, "The function isEveryoneHere
returns true
if Alan
, Jeff
, Sarah
, and Ryan
are properties on the users
object");'
- text: 'The function isEveryoneHere
returns false
if Alan
, Jeff
, Sarah
, and Ryan
are not properties on the users
object'
testString: 'assert((function() { delete users.Alan; delete users.Jeff; delete users.Sarah; delete users.Ryan; return isEveryoneHere(users) })() === false, "The function isEveryoneHere
returns false
if Alan
, Jeff
, Sarah
, and Ryan
are not properties on the users
object");'
```