关于数组技巧的总结

var arr = [‘a‘,‘a‘,‘a‘,‘a‘,‘b‘,‘c‘,‘d‘,‘b‘,‘a‘,‘e‘];
Array.prototype.distinct = function(){
    var ret = [];
    for (var i=0; i < this.length; i++){
        for (var j = i+1; j<this.length;){
            if (this[i] === this[j]){
                ret.push(this.splice(j, 1)[0]);
            } else{
                j++;
            }
        }
    } 
  return ret;
}
alert(arr.distinct());//[a,a,a,a,b]

var arr = [‘a‘,‘a‘,‘a‘,‘a‘,‘b‘,‘c‘,‘d‘,‘b‘,‘a‘,‘e‘];

//原型方法
Array.prototype.unique = function() {
    var o = {}, r = [];  //o哈希表, r为临时数组
    for (var i = 0; i < this.length; i++){
         var v = this[i];
         if (!o[v]){  //判断如果表中没有当前项
            o[v] = true;  //就存入hash表
            r.push(v);   //把当前数组的当前项push到临时数组里面
         }
    }
     return r;
}
alert(arr.unique());[a, b, c , d, e]


//传参函数方法

function unique(arr) {
var result = [], hash = {};
for (var i = 0, elem; (elem = arr[i]) != null; i++) {
if (!hash[elem]) {
result.push(elem);
hash[elem] = true;
}
}
return result;
}

alert(unique(arr))

function count(arr, element){
   var count = 0;
   for (i = 0; i < arr.length; i++){
        if (arr[i] == element){count++}
   }
    alert(count)
}
var arr = new Array(1,2,22,3,5,3,2,6,3);
count(arr, 2)