举例
数组 [1,1,7,4] 去重，并且去掉重复的选项为 [7,4]
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
</head>
<body>
<script>
Array.prototype.unique3 = function(){
var res = [];
var json = {};
var count = 0 ;
var obj = {};
for(var i = 0; i < this.length; i++){
if(!json[this[i]]){ //未存
res.push(this[i]);
json[this[i]] = ++count;
}else{ //已存
if(!obj[this[i]]){ //首次
obj[this[i]] = 1;
for(var j=0;j<res.length;j++){
if(res[j]==this[i]){
res.splice(j,1)
}
}
}
}
}
return res;
}
var arr = [1,1,7,4,7];
console.log(arr.unique3());
</script>
</body>
</html>
原文：http://www.cnblogs.com/sunjingxin/p/6932094.html