如何为对象数组中相邻同Quantity元素添加Count统计字段？

要实现仅统计相邻相同Quantity值的元素数量并添加Count字段，可以按照以下逻辑编写代码：

代码实现 #

let myData = [
    {
        Name: 'Section 1', 
        Details:[
            { Product: 'Ballpen', Quantity: 120},
            { Product: 'Pencil', Quantity: 120},
            { Product: 'Marker', Quantity: 80},
            { Product: 'Highlighter', Quantity: 120}
        ]
    },
    {
        Name: 'Section 2', 
        Details:[
            { Product: 'Paper', Quantity: 40},
            { Product: 'Bond Paper', Quantity: 75},
            { Product: 'Colored Paper', Quantity: 75},
            { Product: 'Oslo paper', Quantity: 40}
        ],
    }
];

// 处理每个分区的数据
myData.forEach(section => {
    const details = section.Details;
    if (details.length === 0) return;

    // 第一步：标记每个相邻分组的数量
    const groupCounts = [];
    let currentQty = details[0].Quantity;
    let currentCount = 1;

    for (let i = 1; i < details.length; i++) {
        if (details[i].Quantity === currentQty) {
            currentCount++;
        } else {
            // 把当前分组的数量重复对应次数存入数组
            for (let j = 0; j < currentCount; j++) {
                groupCounts.push(currentCount);
            }
            currentQty = details[i].Quantity;
            currentCount = 1;
        }
    }
    // 处理最后一个分组
    for (let j = 0; j < currentCount; j++) {
        groupCounts.push(currentCount);
    }

    // 第二步：给每个元素添加Count字段
    details.forEach((item, index) => {
        item.Count = groupCounts[index];
    });

    // 按要求格式输出到控制台
    console.log(`${section.Name} : {`);
    details.forEach(item => {
        console.log(`    [ Product = '${item.Product}', Quantity = ${item.Quantity} , Count = ${item.Count}],`);
    });
    console.log('},');
});

逻辑说明 #

1. 分组统计：遍历Details数组，跟踪当前连续的Quantity值和计数，遇到不同值时，将当前计数重复对应次数存入groupCounts，确保每个元素对应自己所在分组的数量。
2. 添加字段：将groupCounts中的值依次赋值给每个元素的Count属性。
3. 格式输出：按照你需要的结构打印处理后的数据。

运行结果 #

控制台会输出：

Section 1 : {
    [ Product = 'Ballpen', Quantity = 120 , Count = 2],
    [ Product = 'Pencil', Quantity = 120 , Count = 2],
    [ Product = 'Marker', Quantity = 80 , Count = 1],
    [ Product = 'Highlighter', Quantity = 120 , Count = 1],
},
Section 2 : {
    [ Product = 'Paper', Quantity = 40 , Count = 1],
    [ Product = 'Bond Paper', Quantity = 75 , Count = 2],
    [ Product = 'Colored Paper', Quantity = 75 , Count = 2],
    [ Product = 'Oslo paper', Quantity = 40 , Count = 1],
},

处理后的myData中每个Details元素都新增了Count字段，可直接用于表格渲染。

内容的提问来源于stack exchange，提问作者Keyboard Corporation