Question

js怎样判断数组中某个元素个数

Answer 1

js判断数组中某个元素个数实例代码
var arr = [1,2,1];
var map = {};
for(var i = 0; i < arr.length; i++){
var ai = arr[i];
if(!map[ai]){
map[ai] = 1;
}else{
map[ai]++;
}
}
console.log(map);

Answer 2

var array = [1，2，3，2，3，3]；
var num = array.filter(function(n){
return n === 3；
}).length；

Answer 3

<script>
var arr = [1, 5, 84, 4894, 44, 45, 454, 444, 515, 3, 4, 84, 4894, 44, 45, 454, 444, 515, 3, 4, 6, 6, 6, 6, 4];
for (var i = 0; i < arr.length; i++) {
if (arr.indexOf(arr[i]) == i) {
var num = 1;
for (var j = i + 1; j < arr.length; j++) {
if (arr[i] === arr[j]) {
num++;
}
}
console.log(arr[i] + "出现的次数是：" + num)
}
}
</script>