ES6数据分组

  itemgroupby(arr, key) {
    let newarr = [],
        types = {},
        newitem, i, j, cur;
    for (i = 0, j = arr.length; i < j; i++) {
        cur = arr[i];
        if (!(cur[key] in types)) {
            types[cur[key]] = { type: cur[key], data: [] };
            newarr.push(types[cur[key]]);
        }
        types[cur[key]].data.push(cur);
    }
    return newarr;
}