M101 HW31 Verify script for mongo-shell without using aggregate

hw31verifyXP.js

// for mongo shell
// verify homework 3-1 without using aggregate (for Windows XP)
// "provide the identity of the student with the highest average in the class"

var maxAvg = 0;
var maxAvgId = 0;

// loop per student, calculate its' average and compare
var cursor = db.students.find();
while ( cursor.hasNext() ) {
    var doc = cursor.next();
    var sum = 0, count = 0;
    // sum up all scores
    for ( var i=0; i<doc.scores.length; i++ ) {
        sum += doc.scores[i].score;
        count++;
    }
    if ( sum/count > maxAvg ) {
        maxAvg = sum/count;
        maxAvgId = doc._id;
    }
}; // loop students

print("result:");
print("_id: "+maxAvgId);
print("average: "+maxAvg);