sumSeq.js

var _ = require('lodash');

function sumSeq(data) {
    var groups = _(data).groupBy('group').map(function(value) {
        return {
            members: _.orderBy(value, ['seq'], ['desc']),
            sumSeq: _.sumBy(value, 'seq')
        };
    }).orderBy(['sumSeq'], ['desc']).value();
    
    _.forEach(groups, function(value) {
        console.log(value.members[0].group + " " + value.sumSeq + ": " +
                    value.members[0].name + "(" + value.members[0].seq + ")");
    });
}

sumSeq([
	{"name": "Man", "group": "A",  "seq": 8},
	{"name": "John", "group": "A",  "seq": 1},
	{"name": "Dex", "group": "B",  "seq": 2},
	{"name": "Bomb", "group": "A",  "seq": 5},
	{"name": "Joii", "group": "C",  "seq": 7},
	{"name": "New", "group": "B",  "seq": 3},
	{"name": "Keng", "group": "B",  "seq": 4},
	{"name": "Tan", "group": "C",  "seq": 6}
]);

/*
 * Should print:
 * A 14: Man(8)
 * C 13: Joii(7)
 * B 9: Keng(4)
 */