en.javascript.info/1-js/3-object-basics/7-array/1-item-value/solution.md

The result is 4:

let fruits = ["Apples", "Pear", "Orange"];

let shoppingCart = fruits;

shoppingCart.push("Banana");

*!*
alert( fruits.length ); // 4
*/!*

That's because arrays are objects. So both shoppingCart and fruits are the references to the same array.