This list showcases some of the most popular JavaScript algorithms, from simple string manipulations to classic recursive solutions and efficient searching techniques. Each snippet demonstrates a fundamental concept often encountered in coding interviews and real-world development.
Note: Popularity is based on common interview topics, educational resources, and usage in developer communities.
function reverseString(str) {
return str.split("").reverse().join("");
}
console.log(reverseString("hello")); // Output: "olleh"Explanation: Reverses the characters in a string by splitting, reversing, and joining them back together.
function isPalindrome(str) {
return str === str.split("").reverse().join("");
}
console.log(isPalindrome("racecar")); // Output: trueExplanation: Determines if a string reads the same backward as forward using string reversal.
function binarySearch(arr, target) {
let left = 0,
right = arr.length - 1;
while (left <= right) {
const mid = Math.floor((left + right) / 2);
if (arr[mid] === target) return mid;
if (arr[mid] < target) left = mid + 1;
else right = mid - 1;
}
return -1;
}
console.log(binarySearch([1, 2, 3, 4, 5], 4)); // Output: 3Explanation: Searches for a target in a sorted array using a divide-and-conquer approach (Time complexity: O(log n)).
function fibonacci(n) {
if (n <= 1) return n;
return fibonacci(n - 1) + fibonacci(n - 2);
}
console.log(fibonacci(6)); // Output: 8Explanation: Generates the nth Fibonacci number recursively by summing the two preceding numbers.
function factorial(n) {
if (n === 0) return 1;
return n * factorial(n - 1);
}
console.log(factorial(5)); // Output: 120Explanation: Calculates the factorial of a number recursively by multiplying it with decremented values.
function isPrime(num) {
if (num <= 1) return false;
for (let i = 2; i <= Math.sqrt(num); i++) {
if (num % i === 0) return false;
}
return true;
}
console.log(isPrime(7)); // Output: trueExplanation: Checks if a number is prime by testing divisibility up to its square root.
function findMax(arr) {
return Math.max(...arr);
}
console.log(findMax([1, 2, 3, 4, 5])); // Output: 5Explanation: Finds the largest number in an array using the Math.max function and the spread operator.
function mergeSortedArrays(arr1, arr2) {
let merged = [], i = 0, j = 0;
while (i < arr1.length && j < arr2.length) {
if (arr1[i] < arr2[j]) {
merged.push(arr1[i]);
i++;
} else {
merged.push(arr2[j]);
j++;
}
}
return merged.concat(arr1.slice(i)).concat(arr2.slice(j));
}
console.log(mergeSortedArrays([1, 3, 5], [2, 4, 6])); // Output: [1, 2, 3, 4, 5, 6]Explanation: Merges two sorted arrays into one sorted array by comparing elements sequentially.
function bubbleSort(arr) {
for (let i = 0; i < arr.length; i++) {
for (let j = 0; j < arr.length - i - 1; j++) {
if (arr[j] > arr[j + 1]) {
[arr[j], arr[j + 1]] = [arr[j + 1], arr[j]];
}
}
}
return arr;
}
console.log(bubbleSort([5, 3, 8, 4, 2])); // Output: [2, 3, 4, 5, 8]Explanation: Sorts an array by repeatedly swapping adjacent elements if they are in the wrong order (Time complexity: O(n²)).
function gcd(a, b) {
if (b === 0) return a;
return gcd(b, a % b);
}
console.log(gcd(48, 18)); // Output: 6Explanation: Uses the Euclidean algorithm to compute the greatest common divisor of two numbers (Time complexity: O(log min(a, b))).