Best way to query back unique attribute values in a javascript array of objects?

Question

What would be the best (or fastest) way to find all the possible values of "foo" in the following example array.

var table = [
    {foo: 0, bar:"htns", stuff:123},
    {foo: 2, bar:"snhn", stuff:156},
    {foo: 5, bar:"trltw", stuff:45},
    {foo: 5, bar:"lrctm", stuff:564},
    //few thousand lines later
    {foo: 2596, bar:"cns", stuff:321},
    {foo: 2597, bar:"gcrl", stuff:741}
];

Answer 1

Loop through the array and put the values in a hash (object). It is a O(n) algorithm.

var result = {};
for(var i=0; i<table.length; i++) {
    result[table[i].foo] = 1; //the value can be anything
}

//now read back the unique values
for (i in result) {
    if (result.hasOwnProperty(i)) { 
        console.log(i);
    }
}

Answer 2

This is a typesafe version of Chetan's answer:

var result = {};
for(var i = 0; i < table.length; ++i) {
    var value = table[i].foo;
    result[(typeof value) + ' ' + value] = value;
}

for(id in result) {
    if(result.hasOwnProperty(id)) { 
        console.log(result[id]);
    }
}

It will still break for objects, though: as long as the toString() method hasn't been overwritten, they all share the string representation '[object Object]'.