JavaScript: Count the occurrences of a value in an array
JavaScript fundamental (ES6 Syntax): Exercise-70 with Solution
Write a JavaScript program to count the occurrences of 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
const countOccurrences = (arr, val) => arr.reduce((a, v) => (v === val ? a + 1 : a), 0);
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 1));
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 2));
console.log(countOccurrences([1, 1, 2, 1, 2, 3], 3));
Sample Output:
3 2 1
Pictorial Presentation:
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-70-1 by w3resource (@w3resource) on CodePen.
Improve this sample solution and post your code through Disqus
Previous: Write a JavaScript program to group the elements of an array based on the given function and returns the count of elements in each group.
Next: Write a JavaScript program to create a deep clone of an object.
What is the difficulty level of this exercise?
Test your Programming skills with w3resource's quiz.
JavaScript: Tips of the Day
Converts a string to title case
Example:
const toTitleCase = str => str .match(/[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g) .map(x => x.charAt(0).toUpperCase() + x.slice(1)) .join(' '); console.log(toTitleCase('some_database_field_name')); // 'Some Database Field Name' console.log(toTitleCase('Some label that needs to be title-cased')); // 'Some Label That Needs To Be Title Cased' console.log(toTitleCase('some-package-name')); // 'Some Package Name' console.log(toTitleCase('some-mixed_string with spaces_underscores-and-hyphens')); // 'Some Mixed String With Spaces Underscores And Hyphens'
Output:
"Some Database Field Name" "Some Label That Needs To Be Title Cased" "Some Package Name" "Some Mixed String With Spaces Underscores And Hyphens"
- New Content published on w3resource:
- HTML-CSS Practical: Exercises, Practice, Solution
- Java Regular Expression: Exercises, Practice, Solution
- Scala Programming Exercises, Practice, Solution
- Python Itertools exercises
- Python Numpy exercises
- Python GeoPy Package exercises
- Python Pandas exercises
- Python nltk exercises
- Python BeautifulSoup exercises
- Form Template
- Composer - PHP Package Manager
- PHPUnit - PHP Testing
- Laravel - PHP Framework
- Angular - JavaScript Framework
- Vue - JavaScript Framework
- Jest - JavaScript Testing Framework