我想减少items数组，使其包含一个带有更新数量的“Apple”元素。 下面的代码返回正确的缩减数组，但它也改变了原始的items数组，我不明白为什么。

null

const items = [
    {name: "apples", qty: 1},
    {name: "bananas", qty: 1},
    {name: "apples", qty: 3}
];

const reducedItems = items.reduce(function(newArray, currentItem) {
    const indexForCurrentItem = newArray.findIndex(
        ({name}) => name === currentItem.name
    );
    // if current item is not in newArray, add it
    // but if it is already in newArray, update its quantity property there
    indexForCurrentItem === -1
        ? newArray.push(currentItem)
        : newArray[indexForCurrentItem].qty += currentItem.qty;
    return newArray;
}, []);

console.log(reducedItems);
console.log(items);

// reducedItems is correct: [{name: "apples", qty: 4}, {name: "bananas", qty: 1}]

// but items is now:
//  [
//      {name: "apples", qty: 4},
//      {name: "bananas", qty: 1},
//      {name: "apples", qty: 1}
//  ]

null