使用节点j迭代json数组对象

Question

我有一个任务来遍历包含json数组的复杂json文件。我无法从json文件访问数组对象。

I need to access the particularly the class-name object from the json file.

classdetail.json

[ [ { "student" : [ 
    { 
    "name" : "AAaa", 
    "class-name" : "A", 
    "grade-label" : "AA" }, 
    { 
    "name" : "AAbb", 
    "class-name" : "A", 
    "grade-label" : "AB" }, 
    { 
    "name" : "AAcc", 
    "class-name" : "A", 
    "grade-label" : "AB" }, 
    { 
    "name" : "AAdd", 
    "class-name" : "B", 
    "grade-label" : "AA" } ], 
     "Average" : 2.5 }, 

     { 
    "student" : [ 
     { 
    "name" : "BBaa", 
    "class-name" : "B", 
    "grade-label" : "AB" }, 
     { 
    "name" : "BBbb", 
    "class-name" : "B", 
    "grade-label" : "AA" }, 
     { 
    "name" : "BBcc", 
    "class-name" : "B", 
    "grade-label" : "AA" }, 
     { 
    "name" : "BBdd", 
    "class-name" : "B", 
    "grade-label" : "AA" } ], 
     "Average" : 2.5 } ] ] 

iterate.js

var fs = require('fs'); 
var express = require('express'); 
var http = require('http'); 
var publicApis; 
var item; 
var subItem; 


classmem = JSON.parse(fs.readFileSync("classdetail.json", "utf8")); 



for (item in classmem) { 
    for (subItem in classmem[item]) { 
    console.log(classmem[item][subItem]); 
    } 
} 

Answer 1

for (item in classmem) { 
    for (subItem in classmem[item]) { 
    var student = classmem[item][subItem].student; 
    for (row in student) { 
     console.log(student[row]['class-name']); 
    } 
    } 
} 

但了解Array.forEach。

Answer 2

for...in迭代以任意顺序的对象属性。它可能不是您想要用于数组的按顺序存储项目的数组。 （不过，在这种情况下工作）

尝试Array.forEach()：

// iterate over `classmem` 
classmem.forEach(function(element, index, array) { 
    // iterate over classmem[index], which is an array too 
    element.forEach(function(el, idx, arr) { 
    // classmem[index][idx] contains objects with a `.student` property 
    el.student.forEach(function(e, i, a) { 
     console.log(e["name"], e["class-name"], e["grade-label"]); 
    }); 
    }); 
}); 

Answer 3

首先检查数值数组，然后进入到“类名”值

for (item in classmem) { 
    for (subItem in classmem[item]) { 
     **if (typeof classmem[item][subItem] === 'object') { 
      classmem[item][subItem].forEach(function (val, ind) { 
       console.log(val['class-name']); 
      }); 
     }** 
    } 
}