var mass = []
for (let i = 0; i < 100; i++) {
    mass[i] = Math.round(Math.random() * 10)
}
var occurrences = [];
var parsed = [];
for (let i = 0; i < mass.length; i++) {
    if (parsed.hasOwnProperty(mass[i])) {
        continue
    }
    parsed[mass[i]] = 1
    for (let j = 0; j < mass.length; j++) {
        if (mass[i] === mass[j]) {
            occurrences[mass[i]] == undefined ? occurrences[mass[i]] = 1 : occurrences[mass[i]]++
        }
    }
}
var count = -1;
var number;
for (var i = 0; i < occurrences.length; i++) {
    if (occurrences[i] > count) {
        count = occurrences[i];
        number = i;
    }
}
console.log("Мода множества чисел: " + number + "; с количеством совпадений равным: " + count)