從多維對象獲取數組

Question

我試圖從對象中獲取基於id的類數組。 （並將其存儲）

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 

我在做什麼錯在這裏？提前謝謝你的幫助！

Answer 1

你得到使用Array#find方法屬性名，而你試圖讓字符串classes財產，哪些是undefined。因此，您需要使用由Array#find方法返回的屬性名稱從對象獲取屬性值。

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

Answer 2

你只得到鑰匙。 Try：

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);