Discussion on: Daily Challenge #93 - Range Extraction

[Anders]

This is my take on this one, longer code, hopefully easy to read...

function Solution(a) {

    var AddSequenceToString = function (seq, s) {

        if (s) { s += ', '; }
        s += (seq.length >= 3)? seq[0] + '-' + seq[seq.length - 1] : seq.join(', ');
        return s;
    }

    var sequence = [];
    var s = '';

    for (var i = 0; i < a.length; ++i) {

        var n = a[i];

        if (sequence.length == 0 || sequence[sequence.length - 1] == n - 1) { 

            sequence.push(n);

        } else {

            s = AddSequenceToString(sequence, s);
            sequence = [n];
        }
    }

    s = AddSequenceToString(sequence, s);

    return s;
}

And since I am a sucker for benchmarking, I compared it (Chrome 77, Win10) with the other solutions posted so far, 10 000 runs, average of 5 tests with the sample test data:

154 ms for erwzwanderman (first)
59 ms for erwzwanderman (second)
57 ms for La blatte
11 ms for Anders

(NOTE: I added a .join() to La blattes solution as it returns an array, not a string)