To count elements of an array in JavaScript, you can use the “length” property. The “length” property sets or returns the number of elements in an array. The value of a length property is the integer with a positive sign and a value less than 2 to the 32nd power.
Syntax
array.length
To set the length of the array, use the array.length =number syntax.
Return Value
The length property returns a Number, representing the number of elements in the array object.
Example
const netflix = ["Stranger Things", "Money Heist", "Loki", "WandaVision"]
let length = netflix.length
console.log(length)
Output
4
It returns 4, which means the array contains four elements. The length property of an object, an instance of type Array, sets or returns the number of elements in that array.
How to count certain elements in an array
To count certain elements in the array in JavaScript, you can use the “filter()” function with the length property.
const arr = [11, 21, 19, 21, 46]
const elementToCount = 21;
let count = arr.filter(x => x == elementToCount).length
console.log(count)
Output
2
In this example, the “filter()” method creates a new array that only contains elements equal to elementToCount.
Then, we used the filtered array’s length property to get the desired element’s count.
You can generalize this to a function to make it reusable:
function countOccurrences(arr, elementToCount) {
return arr.filter(item => item === elementToCount).length;
}
const arr = [1, 2, 3, 2, 1, 2, 3, 1, 1, 1, 2, 3, 3, 3];
console.log(countOccurrences(arr, 1)); // Output: 6
console.log(countOccurrences(arr, 2)); // Output: 4
console.log(countOccurrences(arr, 3)); // Output: 5
This function takes an array arr and an element elementToCount and returns the count of that element in the array. That’s it.

Krunal Lathiya is a seasoned Computer Science expert with over eight years in the tech industry. He boasts deep knowledge in Data Science and Machine Learning. Versed in Python, JavaScript, PHP, R, and Golang. Skilled in frameworks like Angular and React and platforms such as Node.js. His expertise spans both front-end and back-end development. His proficiency in the Python language stands as a testament to his versatility and commitment to the craft.