Sum object values

Write a function that takes an object (a) as argument. Return the sum of all object values.
function
myFunction
(
a
)
{

return
}
Test Cases:
myFunction({a:1,b:2,c:3})
Expected
6
myFunction({j:9,i:2,x:3,z:4})
Expected
18
myFunction({w:15,x:22,y:13})
Expected
50