javascript get last element in array

1let arr = [1,2,3]
2arr[arr.length - 1] //returns last element in an array

1var colors = ["red","blue","green"];
2var green = colors[colors.length - 1];//get last item in the array

1var array =[1,2,3,4];
2var last= array[array.length-1];

1//im here because the ad

1this = array[array.length - 1];

1//why was this a ad