Simple, generic Vector thinger for JS. Just basic ops.

vec.js

var Vec = decorate({
    add: function(a, b) {return a + b;},
    sub: function(a, b) {return a - b;},
    div: function(a, b) {return a / b;},
    mul: function(a, b) {return a * b;}    
}, function(op) {
  return function() {
    var pos = arguments[0].slice();
    var i, len, arg;
    
    for(i = 1, len = arguments.length; i < len; i++) {
      arg = arguments[i];

      pos = update(pos, isNumber(arg)? [arg, arg]: arg);
    }

    return pos;
  };
  
  function update(pos, arg) {
    return pos.map(function(v, i) {
      return op(v, arg[i]);
    });
  }
});

function decorate(o, fn) {
  var ret = {};

  for(var k in o) if(o.hasOwnProperty(k)) ret[k] = fn(o[k]);
  
  return ret;
}

function isNumber(n) {
  return !isNaN(parseFloat(n)) && isFinite(n);
}

// demo

var a = Vec.add([1, 2], [1, 2]);
var b = Vec.mul([1, 2], [1, 2]);
var c = Vec.mul([1, 2], 0.5);
var d = Vec.sub([1, 2], [2, 1]);

console.log(a, b, c, d);