JavaScript multiple dispatch using predicate functions

dispatcher.js

var nil = 'indicating a nil value';
function reducePredicatePair(reduction, pair) {
  // If no reduction has yet been found and the predicate
  // matches, run the assocated function.
  if(reduction[0] === nil && pair[0].apply(null, reduction[1])) {
    reduction[0] = pair[1].apply(null, reduction[1]);
  }
  return reduction;
}

function dispatcher() {
  // Predicate-function based multiple dispatch.
  // function, [function, function]... -> function

  // The first argument is a fallback function if no other function matches.
  var fallback = arguments[0];
  // The rest arguments are pairs of predicate function + value function.
  var pairs = Array.prototype.slice.call(arguments, 1);

  return function composedDispatcher() {
    var value = pairs.reduce(reducePredicatePair, [nil, arguments])[0];
    return value === nil ? fallback.apply(null, arguments) : value;
  }
}