Javascript array reverse function unexpected behavior

Question

I would like to understand why situation 1 and situation 2 don't return the same results.

Situation 1 :

var array1 = ["1", "2", "3"];
var array2 = array1.reverse();

console.log(array1); // ["3", "2", "1"]
console.log(array2); // ["3", "2", "1"] Why this doesn't work ?

Situation 2 :

var array1 = ["1", "2", "3"];
var array2 = array1;

console.log(array1);           // ["1", "2", "3"]
console.log(array2.reverse()); // ["3", "2", "1"] Why this works ?

Answer 1

In Situation 1

The reverse method transposes the elements of the calling array object in place, mutating the array, and returning a reference to the array.

In Situation 2 you have the same reference. You are printing array1 array before reverse it.

var array1 = ["1", "2", "3"];
var array2 = array1;

console.log(array1);           // [ '1', '2', '3' ]
console.log(array2.reverse()); // [ '3', '2', '1' ]
console.log(array1);           // [ '3', '2', '1' ]

Answer 2

When you call .reverse you are reversing the value, and then returning the array.

var array1 = ["1", "2", "3"]; //Create a new array
var array2 = array1.reverse();//Reverse array1 and assign it to array2

Any changes made to array1 are also reflected in array2 in this case, the confusion arose from the fact that you were printing the value before it was modified.