Round robin scheduler in JavaScript - https://www.npmjs.com/package/roundrobin

roundrobin.js

function(n, ps) {
  const DUMMY = -1;
   var rs = [];                  // rs = round array
    if (!ps) {
      ps = [];
      for (var k = 1; k <= n; k += 1) {
        ps.push(k);
      }
    } else {
      ps = ps.slice();
    }

    if (n % 2 === 1) {
      ps.push(DUMMY); // so we can match algorithm for even numbers
      n += 1;
    }
    for (var j = 0; j < n - 1; j += 1) {
      rs[j] = []; // create inner match array for round j
      for (var i = 0; i < n / 2; i += 1) {
        if (ps[i] !== DUMMY && ps[n - 1 - i] !== DUMMY) {
          rs[j].push([ps[i], ps[n - 1 - i]]); // insert pair as a match
        }
      }
      ps.splice(1, 0, ps.pop()); // permutate for next round
    }
    return rs;
}

roundRobin(6)
[ [ [ 1, 6 ], [ 2, 5 ], [ 3, 4 ] ],
  [ [ 1, 5 ], [ 6, 4 ], [ 2, 3 ] ],
  [ [ 1, 4 ], [ 5, 3 ], [ 6, 2 ] ],
  [ [ 1, 3 ], [ 4, 2 ], [ 5, 6 ] ],
  [ [ 1, 2 ], [ 3, 6 ], [ 4, 5 ] ] ]

and

roundRobin(3,['a','b','c'])
[ [ [ 'b', 'c' ] ],
  [ [ 'a', 'c' ] ],
  [ [ 'a', 'b' ] ] ]

Adapted from this node module on npm.