数组被复制了吗？
重要性：3
这段代码会显示什么？
let fruits = ["Apples", "Pear", "Orange"];
// push a new value into the "copy"
let shoppingCart = fruits;
shoppingCart.push("Banana");
// what's in fruits?
alert( fruits.length ); // ?结果是 4
let fruits = ["Apples", "Pear", "Orange"];
let shoppingCart = fruits;
shoppingCart.push("Banana");
alert( fruits.length ); // 4这是因为数组是对象。因此，shoppingCart 和 fruits 都是指向同一个数组的引用。