CombinationOf2.js

// Combination of 2.
// Took about 1 second with an array with 1000 unique ints
var a = [0,1,2];

var combs = [];
var combinationOf2 = function(a)
{
    var combs = [];   

    var size = a.length;
    for (i = 0; i < size-1; ++i)
    {
        for (j = i+1; j < size; ++j)
        {
            // 
            combs.push(a[i] + '-' + a[j]);
        }
    }
    return combs
}
// Returns [0-1, 0-2, 1-2]
combinationOf2(a);