нахождение количество повторений в числовом массиве

min_most_duplicate.js

var arr = [3, 7, 7, 7, 7,7, 10, 10, 8, 5, 5, 5, 5, 20, 20, 1];

function min_most_duplicate (arr) {
    var result = {},
        max    = 0,
        res;

    arr = arr.slice(0); // make a copy of the array
    arr.sort(function(a, b) { return (a - b); }); // sort it numerically
    console.log(arr);
    for( var i = 0, total = arr.length; i < total; ++i ) {
        var val = arr[i],
        inc = ( result[val] || 0 ) + 1;
        result[val] = inc;

        if( inc > max ) { 
            max = inc;
            res = val;
        }
    }
    return res + ' ' + result[res];
}

console.log( min_most_duplicate (arr) ); // returns 5