sessionize

sessionize.js

function sessionize(nums, threshold) {
    threshold = threshold || 3;

    var i = 0, j = 0, sessions = [];

    while (j < nums.length - 1) {
        if (nums[j + 1] - nums[j] > threshold) {
            sessions.push([nums[i], nums[j]]);
            i = ++j;
        } else {
            ++j;
        }
    }

    sessions.push([nums[i], nums[j]]);

    return sessions;
}

console.log(sessionize([1,2,3,17,18,19,20]));
console.log(sessionize([1,3,17,18,20]));
console.log(sessionize([1,17,30]));
console.log(sessionize([1,3,5,8,9,12,14,16,19,20,22,24,27,28,29,32]));