<script type="text/javascript">
<!--
var str = "adffaafg";
var obj = {},arr = [];
for(var i = 0; i < str.length; i++)
obj[str.charAt(i)] = (obj[str.charAt(i)] != undefined) ? obj[str.charAt(i)] + str.charAt(i) : str.charAt(i);
for(var k in obj) arr.push(obj[k].length);
for(var j in obj){
if(obj[j].length == Math.max.apply(null, arr)){
alert(j + "出现次数为" + obj[j].length);
}
}
//-->
</script>
hash实现