索引列表动态添加数据并排序

最近做项目用到索引列表，这里跟大家分享下我的经验，效率不是最好，大家一起讨论
接口返回数据格式：
{"result":{"code":"200","data":[{"phone":"未知","userId":"D63E526F8BF64FB6AF82E662B997F8FE","userName":"ceshi01","userRealName":"测试账号"},{"phone":"13256441111","userId":"8773107092004B40BB9FD8C159888D96","userName":"dongsheng_ys","userRealName":"dongsheng_ys"},{"phone":"17773069705","qq":"252231478","userId":"C542D82CE9AE4E0CA67E097008E5EC9C","userName":"fangjing6066","userRealName":"方静"},{"phone":"未知","userId":"5EB7CE0783774147A54E69A7E77A8B8A","userName":"fyw1","userRealName":"fyw1"},{"phone":"17773069331","qq":"645708253","userId":"F59788ADA12D42F38955749B10183FD2","userName":"gaomingzhu","userRealName":"高明珠"},{"phone":"17773069730","userId":"42D715F3BCEF47598A874340836A161C","userName":"geshenghua","userRealName":"葛生华"},{"phone":"17773069332","qq":"317268372","userId":"7788347362204F2690274CBA94891771","userName":"lishuang","userRealName":"李双"},{"phone":"17773069330","qq":"1161097955","userId":"2642A854E83140DC9E9C18B2F579FFF4","userName":"liuya","userRealName":"刘涯"},{"phone":"未知","userId":"87AE4788E1E74C5AA7BF214194DAAFEE","userName":"majiao","userRealName":"马姣"},{"phone":"13575009113","userId":"D85D37778F5744C7823D9DE75C2C77F9","userName":"xuzhixia","userRealName":"许志霞"},{"phone":"17773069329","qq":"124912358","userId":"721DB6536501485198F033D371D12A5E","userName":"yangtao","userRealName":"杨涛"},{"phone":"17773069328","qq":"42426382","userId":"851D39149D294A598BE778C30D33CD06","userName":"youxianyi","userRealName":"游险夷"}]}}；
数据是已经排过序的，这样做起来会方便很多。
封装成函数

function wrapContactList(data){  
    var html = "",oldChar = "";  
    mui.each(data,function(index,result){  
        var c = result.userName.substr(0,1);  
        if(c != oldChar){  
            //当前userName与上一个不同则另加一个索引  
            html += '<li data-group="'+c.toUpperCase()+'" class="mui-table-view-divider mui-indexed-list-group">'+c.toUpperCase()+'</li>';  
            oldChar = c;  
        }  
        html += '<li data-userid="'+result.userId+'" data-username="'+result.userName+'" data-phone="'+result.phone+'" class="mui-table-view-cell mui-indexed-list-item">'+result.userRealName+ (result.phone.length>7?"("+result.phone+")":"") +'</li>';  
    });  
    //遍历结束插入数据  
    document.getElementById("contactList").innerHTML = html;  
    //重新实例化索引列表，不然快速查找不生效  
    mui("#list").indexedList();  
}