请实现一个函数用来找出字符流中第一个只出现一次的字符

var res = [];
function Init()
{
    res = [];
}
//Insert one char from stringstream
function Insert(ch)
{
    if( res[ch] ){
        res[ch]++;
    }else{
        res[ch] = 1;
    }
}
//return the first appearence once char in current stringstream
function FirstAppearingOnce()
{
    for( var ch in res ){
        if( res.hasOwnProperty(ch) ){
            if( res[ch] == 1 ){
                return ch;
            }
        }
        
    }
    
    return '#';
}