JavaScript重复元素处理方法分析【统计个数、计算、去重复等】

//将字符串的字符保存在一个hash table中，key是字符，value是这个字符出现的次数
var str = "abcdefgaddda";
var obj = {};
for (var i = 0, l = str.length; i < l; i++) {
 var key = str[i];
 if (!obj[key]) {
 obj[key] = 1;
 } else {
 obj[key]++;
 }
}
/*遍历这个hash table，获取value最大的key和value*/
var max = -1;
var max_key = "";
var key;
for (key in obj) {
 if (max < obj[key]) {
 max = obj[key];
 max_key = key;
 }
}
alert("max:"+max+" max_key:"+max_key);

function GetBytes(str){
 var len = str.length;
 var bytes = len;
 for(var i=0; i<len; i++){
 if (str.charCodeAt(i) > 255) bytes++;
 }
 return bytes;
}
alert(GetBytes("你好,as"));

var arr = [1 ,1 ,2, 3, 3, 2, 1];
Array.prototype.unique = function(){
 var ret = [];
 var o = {};
 var len = this.length;
 for (var i=0; i<len; i++){
 var v = this[i];
 if (!o[v]){
 o[v] = 1;
 ret.push(v);
 }
 }
 return ret;
};
alert(arr.unique());

var arr = '112332454678';
String.prototype.unique = function(){
 var ret = [];
 var o = {};
 var len = this.length;
 for (var i=0; i<len; i++){
 var v = this[i];
 if (!o[v]){
 o[v] = 1;
 } else {
 o[v] = 2;
 }
 }
 for(var k in o){
 if (o[k]==1) {
 ret.push(k);
 };
 }
 return ret;
};
alert(arr.unique());