仅当ID存在于数组中时为字典添加指定键的异常排查

我尝试根据数组中存在的值（同时也是字典键值对中的值）更新字典，但发现当值匹配并为字典添加额外键后，后续所有值也会被更新。尝试在后续出现时删除该键，却会把所有实例中的该键都删掉。

示例代码 #

const dd = {
    somedata : 'hello',
    anotherset: 'bye',
    data : {
        udo: {
            id: 123456789
        }
    }
}

const someId = [987, 654, 123, 567]

const arr = [123, 456]

const someFunc = (arr) => {
    for(const id of someId){
        dd.data.udo.customer_id = id;
        //c
        for(const a of arr){
            if(a === dd.data.udo.customer_id){
                dd.data.udo.test = 'test_account';
                
            } else {
                if('test_account' === dd.data.udo.test){
                    delete dd.data.udo.test;
                }
                console.log(JSON.stringify(dd));
                continue
            }
        }
    } 
}
console.log(JSON.stringify(someFunc(arr)));

实际输出 #

{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":987}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":987}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":654}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":654}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":123}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":567}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":567}}}

期望输出 #

{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":987}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":987}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":654}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":654}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":123,"test":"test_account"}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":567}}}
{"somedata":"hello","anotherset":"bye","data":{"udo":{"id":123456789,"customer_id":567}}}

解决方案 #

问题核心是你一直在修改同一个dd.data.udo对象的引用，所有循环操作的都是同一个对象，导致之前的修改会覆盖或影响后续逻辑。正确的做法是每次遍历someId时，创建一个新的udo对象副本，保证每个循环的对象独立。

修改后的代码如下：

const dd = {
    somedata : 'hello',
    anotherset: 'bye',
    data : {
        udo: {
            id: 123456789
        }
    }
}

const someId = [987, 654, 123, 567]

const arr = [123, 456]

const someFunc = (arr) => {
    for(const id of someId){
        // 每次循环创建新的udo对象副本，基于原对象扩展
        const currentUdo = { ...dd.data.udo, customer_id: id };
        // 检查当前id是否在arr中，决定是否添加test字段
        if(arr.includes(id)){
            currentUdo.test = 'test_account';
        }
        // 生成当前的完整对象
        const currentDd = { ...dd, data: { ...dd.data, udo: currentUdo } };
        // 遍历arr输出两次（对应原逻辑的两次循环）
        for(const a of arr){
            console.log(JSON.stringify(currentDd));
        }
    } 
}
someFunc(arr);

说明 #

1. 使用对象扩展运算符{...}创建原对象的副本，避免修改原引用。
2. 先判断当前id是否在arr中，直接给新对象添加或不添加test字段，不需要后续删除操作。
3. 每个循环生成独立的对象，输出时不会互相干扰，完全符合期望结果。

内容的提问来源于stack exchange，提问作者Emil11