javascript - 如何用 2 "steps": `objectVariable[step1][step2] = result;` 初始化对象变量

Question

原始问题:

我正在尝试创建一个新对象，但插入有点复杂:

我正在一个对象内部生成一个对象。

result = Object.values(window.datas).reduce( (newObj, dataRow) => {
    if ( (user.user_id == dataRow.user_id) && (that.dataResult[dataRow.data_id] !== undefined) && (that.dataResult[dataRow.data_id].length !== 0) ) {
        newObj[that.catToApp[that.dataResult[dataRow.data_id].cat_id].name][that.dataResult[dataRow.data_id].ts] = that.dataResult[dataRow.data_id];
    }
    return newObj;
}, {} );

我收到这个错误:

Error in v-on handler: "TypeError: Cannot set property '2017-02-01' of undefined"

线上:

newObj[that.catToApp[that.dataResult[dataRow.data_id].cat_id].name][that.dataResult[dataRow.data_id].ts] = that.dataResult[dataRow.data_id];

我尝试了什么:

1. 将此行更改为只有一个键对象(而不是 2 个)时(为不需要的结果，但仅用于测试)，它起作用了:

---

newObj[that.catToApp[that.dataResult[dataRow.data_id].cat_id].name] = that.dataResult[dataRow.data_id];

---

1. 我尝试做这样的事情——添加一个临时变量并将结果推送给它，一开始我以为我解决了问题，但在检查了几次之后我注意到结果重复了并且“cat_id” s 正在重复。

---

result = Object.values(window.datas).reduce( (newObj, dataRow) => {
    if ( (user.user_id == dataRow.user_id) && (that.dataResult[dataRow.data_id] !== undefined) && (that.dataResult[dataRow.data_id].length !== 0) ) {

        temp[that.dataResult[dataRow.data_id].ts] = that.dataResult[dataRow.data_id];
        newObj[that.catToApp[that.dataResult[dataRow.data_id].cat_id].app_name] = temp;
    }
    return newObj;

}, {} );
temp = {};

---

主要问题:

以这种方式设置对象变量的正确方法是什么:

objectVariable[step1][step2] = result; 

完整代码:

let that    = this;
let result  = null;
let temp    = {};

this.activeUsers.forEach( user => {

    result = Object.values(window.datas).reduce( (newObj, dataRow) => {
        if ( (user.user_id == dataRow.user_id) && (that.dataResult[dataRow.data_id] !== undefined) && (that.dataResult[dataRow.data_id].length !== 0) ) {
            newObj[that.catToApp[that.dataResult[dataRow.data_id].cat_id].app_name][that.dataResult[dataRow.data_id].ts] = that.dataResult[dataRow.data_id];
        }
        return newObj;
    }, {} );


    if (Object.entries(result).length !== 0) {
        that.usersToDatas[user.user_id] = result;
    }

    temp = {};
});

Answer 1

自 ECMAScript 2015 (ES6) 起，您可以使用 computed property names 声明一个对象:

const step1 = 'firstStep', step2 = 'secondStep';

let obj = {
  [step1]: {
    [step2]: 'value'
  }
};

console.log(obj[step1][step2]);

在循环和对象解构中:

const steps = [
  ['loopA', 'loopA_step1', 'loopA_step2', 'loopA_value'],
  ['loopB', 'loopB_step1', 'loopB_step2', 'loopB_value']
];

let obj = {
  'defaultKeyA': 'defaultValueA', // These pairs will be added in the object each
  'defaultKeyB': 'defautlValueB'  // time the loop will be done, into "loopX".
};

for (let i = 0; i < steps.length; i++) {
  const step = steps[i];
  
  // Creates the key "loopX".
  obj[step[0]] = {
    // Inserts original "obj" content into the new object.
    ...obj,
    
    // Creates the key "loopX_step1" with an object as value.
    [step[1]]: {
      // Creates the key "loopX_step2" with "loopX_value" as value.
      [step[2]]: step[3]
    }
  };
}

console.log(obj);