JavaScript嵌套数据结构中添加关联mainData的计数字段需求

现有嵌套数据结构 #

"mainData": {
    entities: []
},
"data2": {
    entities: [
        {
            name: "mainData"    // entities
        },
        {
            name: "mainData"    // entities
        },
        {
            name: "mainData"    // entities
        },
    ]
},
"data3": {
    entities: [
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
    ]
}

（注：修正了原代码中部分语法错误，如缺失的键值对冒号、多余的末尾冒号，保证数据结构合法）

处理需求 #

为每个与mainData相关的对象添加count字段：

• data2的entities包含3个指向mainData的对象，因此data2的count设为3
• data3的entities包含4个指向data2的对象，每个data2对应3个mainData，因此data3的count设为4*3=12

期望输出结果 #

"mainData": {
    entities: []
},
"data2": {
    count: 3,
    entities: [
        {
            name: "mainData"    // entities
        },
        {
            name: "mainData"    // entities
        },
        {
            name: "mainData"    // entities
        },
    ]
},
"data3": {
    count: 12,
    entities: [
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
        {
            name: "data2"   // entities
        },
    ]
}

内容的提问来源于stack exchange，提问作者YHKdaKING