I would like to know if there is a native javascript code that does the same thing as this:

function f(array,value){
    var n = 0;
    for(i = 0; i < array.length; i++){
        if(array[i] == value){n++}
    }
    return n;
}

I would like to know if there is a native javascript code that does the same thing as this:

function f(array,value){
    var n = 0;
    for(i = 0; i < array.length; i++){
        if(array[i] == value){n++}
    }
    return n;
}

• javascript
• arrays

• 3 In my honest opinion the for loop you have is a lot cleaner than using reduce. There's no single built-in method to do it, the closest you can get is built-in methods that'll loop the array for you. – SeinopSys Commented May 21, 2016 at 16:41
• The function and the loop you provided does what you want it to do. What is the reason you are looking for another method? Is it for performance reasons? Do you have a large array and want to avoid going through the whole array? Knowing what your problem is helps with the answer. – Saeed D. Commented May 21, 2016 at 17:55
• @SaeedD., for counting, you need to inspect every element. – Nina Scholz Commented May 21, 2016 at 18:13
• @Nina, You can also use indexOf to find and count elements. See my working code below. But I like RomanPerekhrest answer and use of filter. – Saeed D. Commented May 21, 2016 at 18:21
• @SaeedD., yes, but it has two loops, one while and one indexof loop. – Nina Scholz Commented May 21, 2016 at 18:24

12 Answers 12

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
  

Another option is to use Array.filter():

count = myArray.filter(x => x === searchValue).length;

You could use reduce to get there:

Working example

var a = [1,2,3,1,2,3,4];

var map = a.reduce(function(obj, b) {
  obj[b] = ++obj[b] || 1;
  return obj;
}, {});

You can also use forEach

let countObj = {};
let arr = [1,2,3,1,2,3,4];

let countFunc = keys => {
  countObj[keys] = ++countObj[keys] || 1;
}

arr.forEach(countFunc);

// {1: 2, 2: 2, 3: 2, 4: 1}

Here is my solution without using an additional object and using reduce:

const occurrencesOf = (number,numbers) => numbers.reduce((counter, currentNumber)=> (number === currentNumber ? counter+1 : counter),0);
occurrencesOf(1, [1,2,3,4,5,1,1]) // returns 3
occurrencesOf(6, [1,2,3,4,5,1,1]) // returns 0
occurrencesOf(5, [1,2,3,4,5,1,1]) // returns 1

You could use the Array filter method and find the length of the new array like this

const count = (arr, value) => arr.filter(val => val === value).length

let ar = [2,2,3,1,4,9,5,2,1,3,4,4,8,5];

const countSameNumber = (ar: any, findNumber: any) => {
    let count = 0;
    ar.map((value: any) => {
        if(value === findNumber) {
            count = count + 1;
        }
    })
    return count;
}


let set = new Set(ar);
for (let entry of set) {
    console.log(entry+":", countSameNumber(ar, entry));
}

const arr = ["a", "a", "a", "b", "b", "b", "b", "c", "c", "c"];
let count = 0;

function countValues(array, countItem) {
  array.forEach(itm => {
    if (itm == countItem) count++;
  });
  console.log(`${countItem} ${count}`);
}
countValues(arr, "c");

This is how I did mine using just a for loop. It's not as sophisticated as some of the answers above but it worked for me.

function getNumOfTimes(arrayOfNums){
    let found = {}
        for (let i = 0; i < arrayOfNums.length; i++) {
            let keys = arrayOfNums[i].toString()
            found[keys] = ++found[arrayOfNums[i]] || 1
        }

    return found
}

getNumOfTimes([1, 4, 4, 4, 5, 3, 3, 3])

// { '1': 1, '3': 3, '4': 3, '5': 1 }

You may want to use indexOf() function to find and count each value in array

function g(array,value){
  var n = -1;
  var i = -1;
  do {
    n++;
    i = array.indexOf(value, i+1);
  } while (i >= 0  );

  return n;
}

let countValue = 0;

Array.forEach((word) => {
  if (word === searchValue) {
    return countValue ++;
  }
});
console.log(`The number of word 'asdf': ${countValue}`);

I used this code to count the number of a given word in a text which was previously converted into an array.

var obj = [];
var array = ['a', 'a', 'a', 'b', 'c', 'c', 'd', 'd', 'd', 'd', 'd', 'd'];

array.forEach(element => {
  let count = 1;
  array.forEach(loopo => {
    if(element == loopo)
     {
       obj[loopo] = count++;
     }
  })
});
console.log(obj);