Match pairs - array based (with typed groups)

matchPairs2.js

'use strict';

var i = 0
  , defender = []
  , attacker = []
  , len = Math.max(defender.length, attacker.length);

function mathPair () {
  return selectName(defender) + ' & ' + selectName(attacker);
}

function selectName (arr) {
  var name = arr[Math.floor((Math.random() * arr.length))];

  if (name === undefined) {
    return '__________';
  } else {
    arr.splice(arr.indexOf(name), 1);
    return name;
  }
}

for (i = 0; i < len; i++)
  console.log('#' + (i + 1) + ' ' + mathPair());