Count number of elements in JavaScript array

// Write a function that takes an array (a) as argument
// Return the number of elements in a
function
myFunction
(
a
)
{

return
}
Test Cases:
myFunction([1,2,2,4])
Expected
4
myFunction([9,9,9])
Expected
3
myFunction([4,3,2,1,0])
Expected
5