JS获取首字母

function pySegSort(arr, empty) {
    if (!String.prototype.localeCompare)
        return null;
    var letters = "*ABCDEFGHJKLMNOPQRSTWXYZ".split('');
    var zh = "阿八嚓哒妸发旮哈讥咔垃痳拏噢妑七呥扨它穵夕丫帀".split('');
    var segs = [];// 存放数据
    var py = [];// 存放首字母
    var res = {};
    var curr;
    $.each(letters, function (i) {
        curr = {
            letter: this,
            data: []
        };
        $.each(arr, function (k, v) {
            if ((!zh[i - 1] || zh[i - 1].localeCompare(v.userName) <= 0) && v.userName.localeCompare(zh[i]) == -1) {
                curr.data.push(this);
            }
        });
        if (empty || curr.data.length) {
            py.push(this);
            segs.push(curr);
            curr.data.sort(function (a, b) {
                return a.userName.localeCompare(b.userName);
            });
        }
    });
    res["segs"] = segs;
    res["py"] = py;
    return res;
}