Question

我试图从对象中获取基于id的classes数组。（并存储）

const objs = {
     "1":{
          "name":"Candice",
          "classes": [00029,00023,00032,000222],
          "id":0002918
     },
     "2":{
           "name":"Clark",
           "classes":[000219,00029,00219],
           "id":00032
         }
}

const objsKeys = Object.keys(objs);
const userClasses = objKeys.find(a => objs[a].id === this.state.userId).classes
console.log(userClasses);

// expect output
[00029,00023,00032,000222]

// but returns
Uncaught TypeError: Cannot read property 'classes' of undefined

我在这里做错了什么？感谢您的帮助！

Answer 1

您使用 Array#find 方法获取属性名称，并且您尝试获取字符串的classes属性，undefined。因此，您需要使用 Array#find 方法返回的属性名称从对象获取属性值。

const userClasses = objs[objKeys.find(a => objs[a].id === this.state.userId)].classes

Answer 2

你只是得到钥匙。尝试：

const objs = {
     "1":{
          "name":"Candice",
          "classes": [00029,00023,00032,000222],
          "id":0002918
     },
     "2":{
           "name":"Clark",
           "classes":[000219,00029,00219],
           "id":00032
         }
}

const objsKeys = Object.keys(objs);

//if you console.log the following, you get the property/key of 2:
console.log(objsKeys.find(a => objs[a].id === 00032))

// you need to use that property to get the object value
const userClasses = objs[objsKeys.find(a => objs[a].id === this.state.userId)].classes
console.log(userClasses);

从多维对象获取数组

2 个答案: