3 Sum problem - Given N integers how many triples sum to exactly zero

gistfile1.js

var numbers = [20,-20, 0, 50, -50, 0];

var len = numbers.length;
var count = 0;

var threeSum = function() {
    for(var i = 0;i < len; i++) {
        for(var j = i + 1;j < len; j++) {
            for(var k = j + 1;k < len; k++) {
                if (numbers[i] + numbers[j] + numbers[k] == 0) {
                    console.log('combination: ', numbers[i], numbers[j], numbers[k]);
                    count++;
                }
            }
        }
    }
    return count;
}

console.log('total: ', threeSum());