Secret Santa Chain Thing

// Modified version of [1] to run in node.js console
// 1: https://jsfiddle.net/B1KMusic/gu4ofjre/3/embedded/result%2Cjs/

// Purpose: to see how high the number of independent chains in a secret santa drawing can get.

function FY_sort(list){
    let len = list.length;
    let sel;

    while(len){
        sel = Math.floor(Math.random() * len--);
        [list[len], list[sel]] = [list[sel], list[len]];
    }

    return list;
}

function exclusive_pop(list, exclude){
    let candidate = list.pop();

    if(candidate !== exclude)
        return candidate;

    list.unshift(candidate);
    return list.pop();
}

function getchain(list){
    let head = list.shift();
    let out = head.slice(0);
    let candidate = null;

    while((candidate = list.find(x => x[0] === out[out.length-1])) !== undefined){
        out.push(candidate[1]);
        list.splice(list.indexOf(candidate), 1);
    }

    return out;
}

function write_chains(list){
    let newlist = list.slice(0);
    let chains = new Array;

    while(newlist.length > 0)
        chains.push(getchain(newlist));

    console.log(`Chains: ${chains.length} / ${list.length}`);
    return chains.length;
}

function runit(names){
    let l1 = names.split(",");
    let l2 = FY_sort(l1.slice(0));
    let l3 = new Array;

    l1.forEach(function(el){
        l3.push([el, exclusive_pop(l2, el)]);
    });

    return write_chains(l3);
}

const max = (a,b) => (a > b ? a : b);

(function(){
    let highest = 0;
    let arr = "abcdefghijklmnopqrstuvwxyz".split("");

    for(let i = 0, l; l = arr.length, i < 6; i++)
        arr.forEach(function(el){
            arr.push(el+arr[l-1]);
        });

    for(let i = 0; i < 1000; i++)
        highest = max(highest, runit(arr.join(",")));

    console.log(`Highest number of chains after 1,000 runs: ${highest}`);
}());