The .push
method returns the new length of the array, not the array itself! By setting newList
equal to [1, 2, 3].push(4)
, we set newList
equal to the new length of the array: 4
.
Then, we try to use the .push
method on newList
. Since newList
is the numerical value 4
, we cannot use the .push
method: a TypeError is thrown.