JSON data to calculate the total attendance in percentage?

I have this attendance data for a particular student. If he was present then marked 1 else marked 0 in the respected subject. How I can calculate the total attendance out of it. Please help me out...

    {
      "CGMM": {
        "17:4:2023": 1,
        "19:4:2023": 0
      },
      "CNS": {
        "17:4:2023": 1
      },
      "ML": {
        "17:4:2023": 1,
        "16:4:2023": 1
      }
    }

I need that I can count all those key-value pair which has a value equals 1 and then divide it by total no. of key-value pairs exist which I am finding by:

        const attendenceInML = Object.keys(student.ML).length;
        const attendenceInSEA = Object.keys(student.SEA).length;
        const attendenceInCGMM = Object.keys(student.CGMM).length;
        const attendenceInCNS = Object.keys(student.CNS).length;
        const total = attendenceInML+ attendenceInSEA+ attendenceInCGMM+ attendenceInCNS;

and then multipy the resultant with 100 to get the total attendance in percentage, but I don't know how to fetch only those key-value pairs count which has value as 1. Please help me.

The format is pretty terrible, but you can still iterate over objects with for in syntax:

const data = JSON.parse(input);

let totalClasses = 0;
let attendedClasses = 0;

for (const subject in data) {
  if (data.hasOwnProperty(subject)) { //So that we don't get a runtime error if the object is empty
    const dates = data[subject];
    for (const date in dates) {
      if (dates.hasOwnProperty(date)) {
        totalClasses++;
        attendedClasses += dates[date];
      }
    }
  }
}

const attendancePercentage = (attendedClasses / totalClasses) * 100;

You can reduce the data and calculate sum/average with it. Something like:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const data = {
  "CGMM": {
    "17:4:2023": 1,
    "19:4:2023": 0
  },
  "CNS": {
    "17:4:2023": 1
  },
  "ML": {
    "17:4:2023": 1,
    "16:4:2023": 1
  }
};
const totalAttendance = Object.values(data)
  .reduce( (acc, v) => acc.concat(Object.values(v)), [] );
const sum = totalAttendance.reduce( (acc, v) => acc + v, 0 );
const attendance = sum / totalAttendance.length * 100;
console.log( `sum of value 1: ${sum}\nattendance percentage: ${
  attendance}%` );

<!-- end snippet -->

You can do it with an combination of Object.entries, Object.values and .reduce

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

let student = {
      "CGMM": {
        "17:4:2023": 1,
        "19:4:2023": 0
      },
      "CNS": {
        "17:4:2023": 1
      },
      "ML": {
        "17:4:2023": 1,
        "16:4:2023": 1
      }
    }
    
    
let result = Object.entries(student)
               .reduce((prev, [key, objValue]) => prev + Object.values(objValue)
               .reduce((prev,curr) => prev + curr,0),0)

console.log(result)

<!-- end snippet -->