计算数组中每个数字出现的次数

var arr = [12,31,42,54,65,12,31,12,42,22];//统计个数var arr2 = {};arr.forEach(function(item){    if(arr2[item]){        arr2[item] += 1;    }else{        arr2[item] = 1;    }})console.log(arr2);