Callback

function.js

var assignTeamMarks = function(idNo, cb) {
	var fetchTeamID =
		"SELECT teamId FROM " +
		tables.team +
		" WHERE memberID = '" +
		idNo +
		"'";

	connection.query(fetchTeamID, function(err, rows, fields) {
		//if(rows.length!=0)
		{
			console.log(rows);
			teamID = rows[0];
			console.log(teamID.teamId);
			teamID = teamID.teamId;
			var fetchMemberID =
				"SELECT * FROM " +
				tables.team +
				"  WHERE teamId = '" +
				teamID +
				"'and memberID <>'" +
				idNo +
				"'";

			connection.query(fetchMemberID, function(err, rows, fields) {
				//if(rows.length!=0)
				{
					console.log(rows);
					memberID = rows[0].memberID;
					var fetchMemberMarks =
						"SELECT * FROM " +
						tables.evaluation +
						"  WHERE memberID = '" +
						memberID +
						"' or memberID = '" +
						idNo +
						"'";
					connection.query(fetchMemberMarks, function(
						err,
						rows,
						fields
					) {
						console.log(rows);
						var data1 = rows[0],
							data2 = rows[1];
						console.log(data2);
						if (data1.marks >= data2.marks) {
							assignMarks = data1.marks;
							id = data2.memberID;
							returnVal = {
								HighestMemMarks: data1.marks,
								OtherMemMarks: data2.marks,
								teamMarks: assignMarks
							};
						} else {
							assignMarks = data2.marks;
							id = data1.memberID;
							returnVal = {
								HighestMemMarks: data2.marks,
								OtherMemMarks: data1.marks,
								teamMarks: assignMarks
							};
						}
						console.log(assignMarks);

						var assign =
							"UPDATE " +
							tables.evaluation +
							" SET marks='" +
							assignMarks +
							"' WHERE memberID='" +
							memberID +
							"'";
						connection.query(assign, function(err, rows, fields) {
							if (err) console.log(err);
              cb(returnVal);
						});
					});
				}
			});
		}
	});
};

test.js

const assert = require('chai').assert;

const app = require('../indexnew');

// Results
var assignTeamMarks= app.assignTeamMarks("2016a7ps01g", function(val){
  //Test cases may be written here.
});