在javascript中循环遍历数组中的对象

Posted 2023-02-22

【中文标题】在javascript中循环遍历数组中的对象

【英文标题】：Looping over objects in an array in javascript

【发布时间】：2018-07-10 01:24:15

【问题描述】：

我对编码还很陌生。我确实搜索了论坛，但找不到我要解决的问题的答案。我写了一个基本的节点应用程序。它将用于跟踪公立学校系统的课后健身计划的效果。每次访问该计划后，学生都会回答一系列问题。教师查看数据以评估该计划。数据存储在 MongoDB 集合中：

 var visitSchema = mongoose.Schema(
    userid: String,
    date: String,
    activitylist: String,
    presession: String,
    health: String,
    bestpart: String,
    worstpart: String,
    postsession: String,
    approved: 
        type: Boolean,
        default: false
    
 );

我正在使用 d3 尝试显示一些图表，以帮助教师进行分析。这将包括报告与数组中某些项目相关的指标。例如，学生参加了多少次列出的 4 项活动中的一项，看看是否没有被利用。另一个是会前、会后和健康项目，因为这些项目来自无线电输入，是四个选项之一。 我成功地将 mongoDB 数据拉入控制台。

这里有一些访问示例：

    ["_id":"5a56c70d4035a90aafbe99f2","date":"Wed Jan 10 2018 20:08:13 GMT-0600 (CST)","userid":"5a54270477a5d3ff63803879","activitylist":"swimming","presession":"ok","bestpart":"water","worstpart":"splashing","postsession":"good","__v":0,"approved":true,"_id":"5a66ab728f12a65cadefb117","date":"Mon Jan 22 2018 21:26:42 GMT-0600 (CST)","userid":"5a54270477a5d3ff63803879","activitylist":"yoga","presession":"good","health":"good","bestpart":"hi","worstpart":"there","postsession":"verygood","__v":0,"approved":true,"_id":"5a6d0b815e8791217f50948a","date":"Sat Jan 27 2018 17:30:09 GMT-0600 (CST)","userid":"5a67ee7d0f7d0a0b7fb1ae2f","presession":"good","health":"verygood","bestpart":"good","worstpart":"hag","postsession":"good","__v":0,"approved":false,"_id":"5a6d0b905e8791217f50948b","date":"Sat Jan 27 2018 17:30:24 GMT-0600 (CST)","userid":"5a67ee7d0f7d0a0b7fb1ae2f","presession":"great","health":"good","bestpart":"hi","worstpart":"hello","postsession":"verygood","__v":0,"approved":false,"_id":"5a6d0d80f6d66c225d103783","date":"Sat Jan 27 2018 17:38:40 GMT-0600 (CST)","userid":"5a67ee980f7d0a0b7fb1ae30","activitylist":"basketball","presession":"great","health":"verygood","bestpart":"hi","worstpart":"hello","postsession":"verygood","__v":0,"approved":false,"_id":"5a6fe540695e704dd125355a","date":"Mon Jan 29 2018 21:23:44 GMT-0600 (CST)","userid":"5a67ee980f7d0a0b7fb1ae30","activitylist":"basketball","presession":"great","health":"good","bestpart":"bas","worstpart":"nas","postsession":"verygood","__v":0,"approved":false]

我还成功地将数据呈现在 d3 图表中。这是我卡住的地方。现在，我正在使用以下代码解析数据并填充图表。下面的示例适用于活动列表项。它遍历数据并计算数据中每个活动的数量：

function constructData(visitData) 
    let data = [ label: "basketball", value: 0 ,  label: "swimming", value: 0 ,  label: "yoga", value: 0 ]
    visitData.forEach(function(visit) 
        console.log(visit.activitylist)

        for (var i = 0; i < data.length; i++) 
            console.log(data[i])
            //if (visit.activitylist in data[i])
            if (visit.activitylist == data[i].label)  data[i].value++ 
        



    )

    //change(data);
    console.log(data);
    return data;

所以这适用于解析数据，但我必须对我想要报告的集合中的每个项目执行类似的操作。我正在寻找一个更全局的函数，我可以将我感兴趣的项目（活动列表、presession 等）传递到其中，或者只是迭代集合中的每个（或一组）项目。我一直在玩下面的这些代码，但还没有让它工作。该数组只是一个简单的数组，因此我可以进行测试。

 var data = [
    'pear': 1,
    'apple': 2
 , 
    'pear': 5,
    'mango': 10
 , 
    'pear': 3,
    'apple': 5,
 ]

 let final = []
 data.forEach((visit) => 
    for (var key in visit) 
        if (visit.hasOwnProperty(key)) 
            //console.log(visit[key], key)
            final.forEach((f) => 
                console.log(f)
                if (f[key]) 
                    f[key]++
                        return;
                

            )
            console.log(key)
            let obj = 
            obj[key] = 0;
            final.push(obj)
        

    

 )
 console.log(final)

因此，对于上述函数的任何建议，可以循环数据以检查数组中的每个项目或我指定的项目，我们将不胜感激。正如我所说，我对此很陌生，所以如果我的措辞不完全清楚，我深表歉意。提前致谢。

【参考方案1】：

看起来您在如何最好地迭代对象属性方面存在冲突。您有很多选择，如果您想使用循环，您可以执行类似 for-in 的操作：

var visitSchema = 
  userid: 'String1',
  date: 'String2',
  activitylist: 'String3',
  presession: 'String4',
  health: 'String5',
  bestpart: 'String6',
  worstpart: 'String7',
  postsession: 'String8',
  approved: 
      type: true,
      default: false
  


for (var x in visitSchema) 
  console.log(x + ' - ' + visitSchema[x]);

虽然使用循环遍历对象和数组肯定没有任何问题错误，但处理此任务的更现代（和巧妙）的方法是将数组方法链接在一起（三大方法是 map、filter并减少）。关于 here 有一篇很棒的文章。

【参考方案2】：

您可以尝试这样来解析数据，而无需使用太多循环。

const temp = []; 
for (const d in this.data) 
        if (this.data[d]) 
          temp.push(
            name: d,
            value: this.data[d],
          );