Count the number of times a same value appears in a javascript array

There might be different approaches for such purpose.
And your approach with for loop is obviously not misplaced(except that it looks redundantly by amount of code).
Here are some additional approaches to get the occurrence of a certain value in array:

• Using Array.forEach method:

    var arr = [2, 3, 1, 3, 4, 5, 3, 1];
  
    function getOccurrence(array, value) {
        var count = 0;
        array.forEach((v) => (v === value && count++));
        return count;
    }
  
    console.log(getOccurrence(arr, 1));  // 2
    console.log(getOccurrence(arr, 3));  // 3
  

• Using Array.filter method:

    function getOccurrence(array, value) {
        return array.filter((v) => (v === value)).length;
    }
  
    console.log(getOccurrence(arr, 1));  // 2
    console.log(getOccurrence(arr, 3));  // 3