var prices = [500, 300, 400, 700],
    names = ['product1', 'product2', 'product3', 'product4'],
    temp = {};
for (var i = 0; i < names.length; i++) {
    temp[names[i]] = prices[i]
};
names.sort(function(a, b) {
    return temp[b] - temp[a]
});
prices.sort(function(a, b) {
    return b - a
});
alert(prices + '\n' + names)

prices= [500, 300, 400, 700];
names = ['product1', 'product2', 'product3', 'product4'];

binding={}
 for (i in prices){
  if(prices.hasOwnProperty(i))
  binding[prices[i]]=names[i]
}
delete i
binding=[].sort.apply(binding)

prices=[]
names=[]
for(i in binding){
if(binding.hasOwnProperty(i)){
   prices.push(i)
   names.push(binding[i])
 }
}
delete i

names=names.reverse()
prices=prices.reverse()
alert([prices, names])