In programming, one of the most common tasks is working with arrays, especially searching for elements and to count the occurrence of a number. Whether you’re preparing for coding interviews or solving real-world problems, mastering array operations is essential. <\/p>\n\n\n\n
In this article, we tackle a simple yet practical challenge: to count the occurrence of a number in an Array using JavaScript<\/p>\n\n\n\n
We’ll walk through a clear problem statement, analyze the input and output requirements, and finally explore a clean solution using built-in JavaScript functions.<\/p>\n\n\n\n
Given a number K and an array of N elements, how often does K appear in the array? If the number is not present at all, return -1.<\/p>\n\n\n\n
You are given:<\/p>\n\n\n\n
Input<\/strong><\/p>\n\n\n\n Output<\/strong><\/p>\n\n\n\n Explanation:<\/strong> If you’re using a coding platform<\/a> to code JavaScript<\/a> that accepts standard input\/output (such as HackerRank<\/a> or CodeChef), the following solution will work as expected:<\/p>\n\n\n\n If you want to learn more about JavaScript and how it enables developers to work seamlessly, consider enrolling in HCL GUVI\u2019s IIT-M Pravartak-certified <\/strong>Full Stack Development Course<\/a> that not only teaches you the basics but also makes you an experienced developer through hands-on projects guided by an actual mentor.\u00a0<\/p>\n\n\n\n\n
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<\/strong> In this example, K is 2, and the array is [1, 2, 3, 5, 7, 8]. The number 2 appears once in the array, so the output is 1.<\/p>\n\n\n\nJavaScript Solution<\/strong><\/h2>\n\n\n\n
const<\/strong> readline = require(‘readline’);
const<\/strong> rl = readline.createInterface({
input: process.stdin,
output: process.stdout
});
let<\/strong> inputLines = [];
rl.on(‘line’, function<\/strong>(line) {
inputLines.push(line);
if<\/strong> (inputLines.length === 2) {
let<\/strong> [n, k] = inputLines[0].split(‘ ‘).map(Number);
let<\/strong> arr = inputLines[1].split(‘ ‘).map(Number);
let<\/strong> count = arr.filter(x => x === k).length;
if<\/strong> (count === 0) {
console.log(‘-1’);
} else<\/strong> {
console.log(count);
}
rl.close();
}
});<\/td><\/tr><\/tbody><\/table>How the Code Works<\/strong><\/h3>\n\n\n\n
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<\/strong> The program reads two lines of input:
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<\/strong> The array is processed using Array.prototype.filter() to count how often K appears.
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