Why deleted the element of the same array when the element is deleted in the other?

var offices = [1,2,3,4,5,6,7,8,9,10];
var offices1 = offices;
for (var i = 0; i < 10; i++) {
 if (true) {
 delete offices1[i];

In the array of offices is also deleted i-th element. Why?
March 19th 20 at 08:22
1 answer
March 19th 20 at 08:24
This is the basic knowledge, objects are assigned by reference, primitive types by value

Find more questions by tags JavaScript