如何将对象合并为一个字符串

Question

Say i have an object like this

```
{
  "ListOfStudents": {
    "-LTzCztVLA0PW-duF-3e": {
      "StudentInfo": {
        "csvTestFile": {
          "2018-12-18": {
            "attendanceDate": "2018-12-18",
            "attendanceStatus": "present"
          },
          "2018-12-19": {
            "attendanceDate": "2018-12-19",
            "attendanceStatus": "absent"
          },
          "2018-12-20": {
            "attendanceDate": "2018-12-20",
            "attendanceStatus": "present"
          }
        }
      }
    },
    "-LTz15VLA0PW-duF-123": {
      "StudentInfo": {
        "csvTestFile": {
          "2018-12-18": {
            "attendanceDate": "2018-12-18",
            "attendanceStatus": "present"
          },
          "2018-12-19": {
            "attendanceDate": "2018-12-19",
            "attendanceStatus": "absent"
          },
          "2018-12-20": {
            "attendanceDate": "2018-12-20",
            "attendanceStatus": "absent"
          }
        }
      }
    },
    "-LTz15VL515W-duF-163": {
      "StudentInfo": {
        "csvTestFile": {
          "2018-12-18": {
            "attendanceDate": "2018-12-18",
            "attendanceStatus": "absent"
          },
          "2018-12-19": {
            "attendanceDate": "2018-12-19",
            "attendanceStatus": "absent"
          },
          "2018-12-20": {
            "attendanceDate": "2018-12-20",
            "attendanceStatus": "absent"
          }
        }
      }
    }
  }
}
```

Here's my code

const names = 'Albert,John,Alex';

saveCSVFile(data) {
const { classUID } = data;
const { currentUser } = firebase.auth();

const student = [];

firebase
  .database()
  .ref(`/users/${currentUser.uid}/ClassAttendance/${classUID}/ListOfStudents`)
  .on('value', snapshot1 => {
    snapshot1.forEach(child => {
      student.push(child.val().StudentInfo);

      const keys = Object.keys(child.val().StudentInfo.csvTestFile);
      const dates = keys.map(key => child.val().StudentInfo.csvTestFile[key]);
      console.log(dates);
    });
  });
}

Here's the console log output

What i wanted is to merge 'attendanceStatus' into one string but for every first object i want to put each names in the string, and for every last object i want to put '\\n' on it and a , (comma) for each attendanceStatus.

Expected Final Output in String:

'Albert,present,absent,present\\n

John,present,absent,absent\\n

Alex,absent,absent,absent\\n'

or may be the output would be like this

'Albert,present,absent,present\\nJohn,present,absent,absent\\nAlex,absent,absent,absent\\n'

I have been thinking on how to do this for a week, but no luck. Please help

Answer 1

I'm not sure if this is what you are asking for but I hope this gets you on the right track.

 let list = { "-LTzCztVLA0PW-duF-3e": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "present" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "present" } } } }, "-LTz15VLA0PW-duF-123": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "present" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "absent" } } } }, "-LTz15VL515W-duF-163": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "absent" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "absent" } } } } }, result = ""; for(let s in list) { let c = list[s].StudentInfo.csvTestFile; //get the object with the dates for(let d in c) { result += c[d].attendanceStatus + ','; //add the status with a comma } result = result.slice(0, result.length -1); //remove the trailling comma result += '\\n'; //add a newline char for every student } console.log(result); //yay

Answer 2

Here is the implementation using map instead:

 let list = { "-LTzCztVLA0PW-duF-3e": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "present" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "present" } } } }, "-LTz15VLA0PW-duF-123": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "present" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "absent" } } } }, "-LTz15VL515W-duF-163": { "StudentInfo": { "csvTestFile": { "2018-12-18": { "attendanceDate": "2018-12-18", "attendanceStatus": "absent" }, "2018-12-19": { "attendanceDate": "2018-12-19", "attendanceStatus": "absent" }, "2018-12-20": { "attendanceDate": "2018-12-20", "attendanceStatus": "absent" } } } } } const names = 'Albert,John,Alex'; let resultString = Object.keys(list).map((l, index) => { let csvTestFiles = list[l].StudentInfo.csvTestFile; return Object.keys(csvTestFiles).map((i, innerIndex) => { let str = innerIndex === 0 ? `${names.split(',')[index]},` : ''; return str + csvTestFiles[i].attendanceStatus; }).join(','); }).join('\\\\n').concat('\\\\n'); // replace with '\\n' if you want the new line instead, concat is just appending last '\\n' to the string console.log(resultString);