请问怎么把YYYY-MM-DD格式的json数据按月份分组？

var data = [{
        "id": 1,
        "flightDate": "2016-05-11"
    }, {
        "id": 2,
        "flightDate": "2016-05-10"
    }, {
        "id": 3,
        "flightDate": "2016-05-09"
    }, {
        "id": 4,
        "flightDate": "2016-04-08"
    }, {
        "id": 5,
        "flightDate": "2016-04-07"
    }, {
        "id": 6,
        "flightDate": "2016-03-06"
    }, {
        "id": 7,
        "flightDate": "2016-03-05"
    }];
    var d = [];
    var a = 0;
    d[a] = [data[0]];
    for(var i=1;i<data.length;i++){
        var t = data[i]['flightDate'].split('-');
        var f = data[i-1]['flightDate'].split('-');
        if(t[1]==f[1]){
            d[a].push(data[i]);
        }else{
            a = a+1;
            d[a] = [];
            d[a].push(data[i]);
        }
    }
    console.log(d);

写的有点low，不知道是不是你想要的
（前提是你的数据是按时间顺序排列出来的）