--- title: "ayan koley (@ayan01) | Hashnode" description: "ayan koley (@ayan01) writes on Hashnode. Read their latest articles and follow their work." url: "https://hashnode.com/@ayan01" --- @ayan01 # ayan koley @ayan01 · Joined February 2025 ### [Understanding asyncHandler in Express.js (with Higher Order Functions)](https://javascript-higher-order-function-hof.hashnode.dev/understanding-asynchandler-in-expressjs-with-higher-order-functions?utm_source=hashnode&utm_medium=feed) ❓ The Problem with Async Route Handlers Express catch synchronous error automatically, but it doesn’t catch error thrown inside async functions. router.post("/login", async (req, res) => { const user = await User.findOne({ email: req.body.email }... 2 min read · [javascript-higher-order-function-hof.hashnode.dev](https://javascript-higher-order-function-hof.hashnode.dev/understanding-asynchandler-in-expressjs-with-higher-order-functions?utm_source=hashnode&utm_medium=feed) [Dec 18, 2025](https://hashnode.com/posts/understanding-asynchandler-in-expressjs-with-higher-order-functions/6943ff55325c97388599126a) ### [JavaScript Higher Order function (HOF)](https://javascript-higher-order-function-hof.hashnode.dev/javascript-higher-order-function-hof?utm_source=hashnode&utm_medium=feed) What is Higher Order Function ? A Higher Order Function is a function that does at least one of the following Takes another function as an argument Return another function as it’s result Importance of Higher Order Function ? Write clean and read... 2 min read · [javascript-higher-order-function-hof.hashnode.dev](https://javascript-higher-order-function-hof.hashnode.dev/javascript-higher-order-function-hof?utm_source=hashnode&utm_medium=feed) [Dec 18, 2025](https://hashnode.com/posts/javascript-higher-order-function-hof/6943feb8e15763f451c48b02) ### [1498\. Number of Subsequences That Satisfy the Given Sum Condition](https://dailyleetcode.hashnode.dev/1498-number-of-subsequences-that-satisfy-the-given-sum-condition?utm_source=hashnode&utm_medium=feed) First understand the the question.. Return non-empty subsequences Sum of the min and max element on this less or equal to target return module 10^9 + 7 Brute Force approach (Generating all subsequences) A straightforward idea is to generate all pos... 3 min read · [dailyleetcode.hashnode.dev](https://dailyleetcode.hashnode.dev/1498-number-of-subsequences-that-satisfy-the-given-sum-condition?utm_source=hashnode&utm_medium=feed) [Jun 29, 2025](https://hashnode.com/posts/1498-number-of-subsequences-that-satisfy-the-given-sum-condition/6861322d58434ead89c8824c) ### [Analyzing Time Complexity of algorithms](https://01tc.hashnode.dev/analyzing-time-complexity-of-algorithms?utm_source=hashnode&utm_medium=feed) What is Time Complexity 🤷‍♂️ Time complexity is the way to describe how long our code might take to run as the amount of input increase. It doesn't measure actual time - it just provide the rough idea of how the performance growth. Best Case → Ω (O... 4 min read · [01tc.hashnode.dev](https://01tc.hashnode.dev/analyzing-time-complexity-of-algorithms?utm_source=hashnode&utm_medium=feed) [May 16, 2025](https://hashnode.com/posts/analyzing-time-complexity-of-algorithms/68278a1b5a368dc7560e6c4f)