Extract keys from Javascript object

// Write a function that takes an object (a) as argument
// Return an array with all object keys
function
myFunction
(
a
)
{

return
}
Test Cases:
myFunction({a:1,b:2,c:3})
Expected
['a','b','c']
myFunction({j:9,i:2,x:3,z:4})
Expected
['j','i','x','z']
myFunction({w:15,x:22,y:13})
Expected
['w','x','y']