js如何判断一组数字是否连续

function arrange(source) {
    var t;
    var ta;
    var r = [];

    source.forEach(function(v) {
        console.log(t, v);   // 跟踪调试用
        if (t === v) {
            ta.push(t);
            t++;
            return;
        }

        ta = [v];
        t = v + 1;
        r.push(ta);
    });

    return r;
}

var arr = [3, 4, 13, 14, 15, 17, 20, 22];
console.log(arrange(arr));
C:\Users\James\Desktop>iojs test.js
undefined 3
4 4
5 13
14 14
15 15
16 17
18 20
21 22
[ [ 3, 4 ], [ 13, 14, 15 ], [ 17 ], [ 20 ], [ 22 ] ]