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const toFixed = (n, fixed) => ~~(Math.pow(10, fixed) * n) / Math.pow(10, fixed);// ExamplestoFixed(25.198726354, 1); // 25.1toFixed(25.198726354, 2); // 25.19toFixed(25.198726354, 3); // 25.198toFixed(25.198726354, 4); // 25.1987toFixed(25.198726354, 5); // 25.19872toFixed(25.198726354, 6); // 25.198726
class LinkedList {constructor() {this.nodes = [];}get size() {return this.nodes.length;}get head() {return this.size ? this.nodes[0] : null;}get tail() {return this.size ? this.nodes[this.size - 1] : null;}insertAt(index, value) {const previousNode = this.nodes[index - 1] || null;const nextNode = this.nodes[index] || null;const node = { value, next: nextNode };if (previousNode) previousNode.next = node;this.nodes.splice(index, 0, node);}insertFirst(value) {this.insertAt(0, value);}insertLast(value) {this.insertAt(this.size, value);}getAt(index) {return this.nodes[index];}removeAt(index) {const previousNode = this.nodes[index - 1];const nextNode = this.nodes[index + 1] || null;if (previousNode) previousNode.next = nextNode;return this.nodes.splice(index, 1);}clear() {this.nodes = [];}reverse() {this.nodes = this.nodes.reduce((acc, { value }) => [{ value, next: acc[0] || null }, ...acc],[]);}*[Symbol.iterator]() {yield* this.nodes;}}const list = new LinkedList();list.insertFirst(1);list.insertFirst(2);list.insertFirst(3);list.insertLast(4);list.insertAt(3, 5);list.size; // 5list.head.value; // 3list.head.next.value; // 2list.tail.value; // 4[...list.map(e => e.value)]; // [3, 2, 1, 5, 4]list.removeAt(1); // 2list.getAt(1).value; // 1list.head.next.value; // 1[...list.map(e => e.value)]; // [3, 1, 5, 4]list.reverse();[...list.map(e => e.value)]; // [4, 5, 1, 3]list.clear();list.size; // 0
const binarySearch = (arr, item) => {let l = 0,r = arr.length - 1;while (l <= r) {const mid = Math.floor((l + r) / 2);const guess = arr[mid];if (guess === item) return mid;if (guess > item) r = mid - 1;else l = mid + 1;}return -1;};binarySearch([1, 2, 3, 4, 5], 1); // 0binarySearch([1, 2, 3, 4, 5], 5); // 4binarySearch([1, 2, 3, 4, 5], 6); // -1
const geometricProgression = (end, start = 1, step = 2) =>Array.from({length: Math.floor(Math.log(end / start) / Math.log(step)) + 1,}).map((_, i) => start * step ** i);geometricProgression(256); // [1, 2, 4, 8, 16, 32, 64, 128, 256]geometricProgression(256, 3); // [3, 6, 12, 24, 48, 96, 192]geometricProgression(256, 1, 4); // [1, 4, 16, 64, 256]
function sortNumbers(arr) {return arr.slice().sort((a, b) => a - b);}const unsortedArray = [4, 1, 9, 6, 3, 5];const sortedArray = sortNumbers(unsortedArray);console.log("Unsorted Numbers:", unsortedArray);console.log("\n");console.log("Sorted Numbers:", sortedArray);
const jwt = require("jsonwebtoken");const authToken = (req, res, next) => {const token = req.headers["x-auth-token"];try {req.user = jwt.verify(token, process.env.ACCESS_TOKEN_SECRET);next();} catch (err) {console.log(err.message);res.status(401).json({ msg: "Error authenticating token" });}};module.exports = authToken;