Can we find count of element in array using javascript?

Question

I want to find Count Of specific element in array using JavaScript for example [2,2,2,3,3,3,3,3] count of 2 is 3 and count of 3 is 5.

Answer 1

var map = {};
var arr = [2, 2, 2, 3, 3, 3, 3, 3];
for (var i = 0; i < arr.length; i++) {
    if (map[arr[i]]) {
        map[arr[i]]++;
    } else {
        map[arr[i]] = 1;
    }
}
for(var key in map){
 console.log("occurence of "+ key+" = "+map[key]);
}

Output:
occurence of 2 = 3
occurence of 3 = 5

Answer 2

Just for fun (works only with strings and numbers).

[2,2,2,3,3,3,3,3].join().match(/3/g).length; // return 5

Answer 3

Something like this?

function searchInArray(someInt, someArray){
    var count = 0;
    for(var i in someArray){
        if(someArray[i] === someInt){
            count++;
        }
    }
    return count;
}
searchInArray(2, [2,2,2,2,2,3,4,4,4,5]);
//returns 5

Answer 4

In pure JavaScript:

function countOccurrences(array) {
    var occurrences = {};
    for (var i = 0, l = array.length; i < l; i++) {
        if (occurrences[array[i]] === undefined) {
            occurrences[array[i]] = 1;
        }
        else {
            occurrences[array[i]]++;
        }
    }
    return occurrences;
}

var test = [2,2,2,2,3,3,3,3,3,4,4,5];

console.log(countOccurrences(test));

Answer 5

Use a loop.

var thisChar;
var thisCharCount;
for (var i = 0; i < yourArray.length; i++) {
    if(yourArray[i] == thisChar)
    thisCharCount++;
}

Depending if you compare to set or dynamic comparable values, use a array.

Answer 6

Use Underscore:

_.groupBy([2,2,2,3,3,3,3,3])
> {2: [2,2,2], 3: [3,3,3,3,3]}

Then count the length of the arrays.

Do it yourself using Array#reduce:

function counts(array) {
    return array.reduce(function(prev, current) {
        prev[current] = (prev[current] || 0) + 1;
        return prev;
    }, {});
}
> counts([2,2,2,3,3,3,3,3]) // {2: 3, 3: 5}

To count occurrences of a specific val:

function count(array, val) {
    for (var i=0, index=0; (index = array.indexOf(val, index)) !==-1;  i++) { }
    return i;
}

Or if you prefer

function count(array, val) {
    var i=0, index=0;
    while ((index = array.indexOf(val, index)) !== -1) { i++; }
    return i;
}

Or perhaps recursively?

function count(array, val) {
    var index = array.indexOf(val);
    return index === -1 ? 0 : count(array.slice(index), val) + 1;
}

Answer 7

Why not using jQuery:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
    var count2 = 0, count3 = 0;
    $.each([2,2,2,3,3,3,3,3], function( index, value ) {
        if(value==2)
            count2++;
        if(value==3)
            count3++;
    });
    alert("2:"+count2);
    alert("3:"+count3);
});