Question

我得到＆＃39; TypeError：无法将undefined或null转换为object＆＃39;尝试访问nodejs中的json对象的长度。

以下是我的数据：

let colleges = JSON.parse(data)

第1步 - 将其解析为nodejs：

app.data.collegeData = data;

第2步 - 将其保存到对话框流程应用数据中：

let collegeLength = Object.keys(app.data.collegeData.college).length;

第3步 - 访问长度：

if ( app.data.collegeData === undefined ){
    app.data.collegeData = [];
}

**Step 1 =>** 

showColleges(college);

**Step 2 =>**

  function showColleges(collegeName){
      if (app.data.collegeData.length === 0){
          getCollegeData().then(buildSingleCollegeResponse(collegeName))
              .catch(function (err){
                  console.log('No college data')
                  console.log(err)
              });
      }
      else{
          buildSingleCollegeResponse(collegeName);
      }
  }

**Step 3 =>**

 function getCollegeData(){
      console.log('Inside get College Data')
      return requestAPI(URL)
          .then(function (data) {
              let colleges = JSON.parse(data)
              if (colleges.hasOwnProperty('college')){
                  saveData(colleges)
              }
              return null;
          })
          .catch(function (err) {
              console.log('No college data')
              console.log(err)
          });
  }

**Step 4 =>**

  function saveData(data){
      app.data.collegeData = data;
      console.log(app.data.collegeData)
  }

**Step 5 =>**

function buildSingleCollegeResponse(collegeName){
      let responseToUser, text;
      //console.log('Data is -> '+ Object.keys(app.data.collegeData.college).length);
      //console.log('Length is -> '+ app.data.collegeData.college.length);
      console.log('Count is -> '+app.data.collegeCount);

      let collegeLength = Object.keys(app.data.collegeData.college).length;

      if ( collegeLength === 0){
          responseToUser = 'No colleges available at this time';
          text = 'No colleges available at this time';
      }
      else if ( app.data.collegeCount < collegeLength ){

          for ( var i = 1; i <= collegeLength; i++)
          {
              console.log('All Colleges:: '+app.data.collegeData.college[i])
              let coll = app.data.collegeData.college[i]
              let name = coll.name
              console.log('checkCollegeExist => College Name:: '+ name)
              console.log('checkCollegeExist => Parameter => College Name:: '+collegeName)

              if(String(name).valueOf() === String(collegeName).valueOf()){
                  responseToUser = 'Yes! CSUF has '+collegeName;
                  text = 'Yes! CSUF has '+collegeName;
              }else{
                  responseToUser = 'CSUF does not teach ' +collegeName+' currently';
                  text = 'CSUF does not teach ' +collegeName+' currently';
              }
          }
      }
      else{
          responseToUser = 'No more colleges';
      }
      if (requestSource === googleAssistantRequest) {
          sendGoogleResponse(responseToUser);
      } else {
          sendResponse(text);
      }
  }

在firebase控制台中出现以下错误：

TypeError：无法将undefined或null转换为object

更新：

以下是代码：

＆＃13;

{{1}}

＆＃13;

Answer 1

这是罪魁祸首：

getCollegeData().then(buildSingleCollegeResponse(collegeName))

调用 buildSingleCollegeResponse(collegeName)然后将其返回值传递到then，就像foo(bar()) 调用 bar并将其返回值传递给foo。

您想将功能传递给then：

getCollegeData().then(() => buildSingleCollegeResponse(collegeName))
// An arrow function  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

请注意，现在从更新后的问题中可以清楚地看出app.data.collegeData.college是数组，因此不需要Object.keys。变化：

let collegeLength = Object.keys(app.data.collegeData.college).length;

简单地

let collegeLength = app.data.collegeData.college.length;

数组具有length属性（默认情况下，非数组对象不具有）。

Answer 2

在发出app.data

之前，您还没有提到app.data.collegeData = data;的值是多少？

如果未定义app.data，您应该尝试app.data = {collegeData: data}

否则否定应用商店的存储。以下作品

app = {};
app.data = {};
app.data.collegeData = data;

app.data.collegeData.college.length

您不需要执行以下操作

let collegeLength = Object.keys(app.data.collegeData.college).length;

更新：请参阅https://jsfiddle.net/dmxuum79/3/

无法获取JSON对象的长度

2 个答案: