javascript - 如何在javascript中按每个元素计算数组元素

Question

可能重复：
如何计算 Javascript 数组中的匹配值

我有元素数组，

array_elements = ["2","1","2","2","3","4","3","3","3","5"];

我想像以下方式计算数组元素，

回答：

2 次 --> 3 次
1 次 --> 1 次
3 次 --> 4 次
4 次 --> 1 次
5 次 --> 1 次

注意：每个值计数应该只打印一次。

Answer 1

var counts = {};

for (var i = 0; i < array.length; i++)
    counts[array[i]] = (counts[array[i]] + 1) || 1;


console.log(counts);

这假设toStringArray 中的项目的表示是可以接受的。例如，它将1被视为与 相同"1"。

鉴于您的示例数组，这将不是问题。

Answer 2

您可以对元素进行排序并遍历它们：

array_elements = ["2", "1", "2", "2", "3", "4", "3", "3", "3", "5"];

array_elements.sort();

var current = null;
var cnt = 0;
for (var i = 0; i < array_elements.length; i++) {
    if (array_elements[i] != current) {
        if (cnt > 0) {
            document.write(current + ' comes --> ' + cnt + ' times<br>');
        }
        current = array_elements[i];
        cnt = 1;
    } else {
        cnt++;
    }
}
if (cnt > 0) {
    document.write(current + ' comes --> ' + cnt + ' times');
}

演示：http: //jsfiddle.net/Guffa/aQsuP/

Answer 3

var array_elements = ["2","1","2","2","3","4","3","3","3","5"];

var result = array_elements.reduce(function(p, c){
    if (c in p) {
       p[c]++;
    } else {
       p[c]=1;
    }
    return p;
}, {});

​console.log(result);​

现场演示。

注意：减少旧浏览器的 shim 需求。

Answer 4

var arr = ["2","1","2","2","3","4","3","3","3","5"];
var k = {};

//push into hashtable
for(i in arr){
 k[arr[i]]=(k[arr[i]]||0)+1; //increments count if element already exists
}

//result
for(var j in k) {
 console.log(j+" comes -> "+k[j]+" times");
}