partialreplace.js

Function.prototype.partial = function() {
    // CODE HERE

    var fn = this, args = Array.prototype.slice.call(arguments);
    return function() {
        var replace = function(arr) {
            var pos = 0;
            return {
                next : function() {
                    return arr[pos++];
                }
            };
        };

        var replacer = replace(Array.prototype.slice.call(arguments));
        var t = [];

        args.forEach(function(arg) {
            if (arg) {
                t.push(arg);
            } else {
                t.push(replacer.next());
            }
        });

        return fn.apply(this, t);
    };
};

var hi = function(a, b, c, d) {
    console.log(a + ' ' + b + ' ' + c + ' ' + d);
};

var f = hi.partial(undefined, '2', undefined, '4');

f('1', '3');

bacana ! my 2cents !

Function.prototype.partial = function() {
  var partialArgs = Array.prototype.slice.call(arguments);
  var fn = this;

  return function() {
    var args = Array.prototype.slice.call(arguments);
    var params = partialArgs.map(function(curr) {
      if (!curr)
        return args.shift();
      else 
        return curr;
    });

    fn.apply(fn, params);
  };
};