javascript 使用节点js迭代json数组对象
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Iterating json array objects using node js
提问by Ananth
I have got a task to iterate through the complex json file that contains json array. I could not access the array object from the json file.
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.
我需要从 json 文件中访问特别是类名对象。
classdetail.json
类详细信息.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
迭代.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]);
}
}
采纳答案by Tomasz Jakub Rup
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']);
}
}
}
But read about Array.forEach.
但请阅读Array.forEach。
回答by ali khabbaz
first check the value is array then access to the "class-name" value
首先检查值是数组然后访问“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']);
});
}**
}
}
回答by Dan O
for...initerates over object properties in arbitrary order. It might not be what you want to use for an array, which stores items in a well-defined order. (though it should work in this case)
for...in以任意顺序迭代对象属性。它可能不是您想要用于以明确定义的顺序存储项目的数组的内容。（虽然它应该在这种情况下工作）
Try 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"]);
});
});
});
