JavaScript: Count the occurrences of a value in an array

JavaScript fundamental (ES6 Syntax): Exercise-70 with Solution

Count Value in Array

Write a JavaScript program to count a value in an array.

• Use Array.prototype.reduce() to increment a counter each time the specific value is encountered inside the array.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define a function 'countOccurrences' that counts the number of occurrences of a value in an array.
const countOccurrences = (arr, val) =>
  arr.reduce((a, v) => (v === val ? a + 1 : a), 0);

// Example usages:
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 1)); // Output: 3
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 2)); // Output: 2
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 3)); // Output: 1

Output:

3
2
1

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-70-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that counts the number of times a specific value appears in an array.
• Write a JavaScript function that uses reduce() to tally occurrences of a given element in an array.
• Write a JavaScript program that searches an array for a target value and returns its frequency count.

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