Step-by-step articles on Scripting Languages, part of our Programming Languages collection.
Showing 20 articles
JavaScript gets a new edition every year. If you learned it a while ago, these additions will make your code shorter and safer. Safer property access const city = user?.address?.city; // undefined instead of a crash const limit = options.limit ?? 20; // only f...
Python 3.14 was released in October 2025. Here are the changes most developers will notice. Template strings (t-strings) A t-string looks like an f-string but produces a Template object instead of a finished string. Libraries can then process the interpolated...
await in a loop runs requests one after another. JavaScript's promise combinators let you run them together and decide how to handle failures. Sequential vs parallel // Slow: each request waits for the previous one for (const id of ids) { results.push(await fe...
uv is a Python package and project manager written in Rust. It replaces pip, pip-tools, virtualenv, pyenv and pipx with one tool, and it's dramatically faster. Install curl -LsSf https://astral.sh/uv/install.sh | sh # or: pipx install uv, brew install uv Start...
sort() , reverse() and splice() change the original array. That causes subtle bugs, especially with React state, where you must not mutate. ES2023 added non-mutating versions. The old trap const scores = [30, 10, 20]; const ranked = scores.sort((a, b) => b - a...
Type hints don't change how Python runs, but editors and type checkers use them to catch bugs and power autocomplete. Modern Python syntax makes them short and readable. The basics def greet(name: str, times: int = 1) -> str: return ", ".join([f"Hello {name}"]...
Grouping a list (orders by status, posts by month, people by team) used to need reduce or lodash. Object.groupBy does it in one line. Object.groupBy const orders = [ { id: 1, status: 'paid', total: 500 }, { id: 2, status: 'pending', total: 250 }, { id: 3, stat...
Both give you classes with typed fields and less boilerplate. The key difference: dataclasses store data, Pydantic validates and converts it. Dataclasses from dataclasses import dataclass, field @dataclass(frozen=True, slots=True) class Money: amount: int # pa...
JavaScript has had Set since ES2015, but combining sets meant converting to arrays and filtering. ES2025 added the classic set operations as methods. The operations const frontend = new Set(['asha', 'ravi', 'meera']); const oncall = new Set(['ravi', 'kiran']);...
asyncio lets one thread wait on many network operations at once. It shines for I/O-heavy work: calling APIs, scraping, chat servers, database queries. The basics import asyncio import httpx async def fetch_status(client: httpx.AsyncClient, url: str) -> int: re...
Array methods create a whole new array at each step. Iterator helpers work on iterators instead and are lazy : values are processed one at a time, only as many as you need. The methods iterator.map(fn) iterator.filter(fn) iterator.take(n) iterator.drop(n) iter...
match looks like a switch statement, but it's more powerful: it can check the shape of data and pull values out of it in one step. Literals and alternatives def http_message(status: int) -> str: match status: case 200 | 201: return "OK" case 404: return "Not f...
Date mixes up dates, times and time zones, months start at 0, and objects are mutable. Temporal is a new built-in API that fixes these problems. It has started shipping in browsers; elsewhere you can use the official polyfill. npm install @js-temporal/polyfill...
pytest is the standard testing tool for Python. Tests are plain functions using plain assert , and pytest's output shows exactly what differed. First tests # test_pricing.py import pytest from pricing import apply_discount def test_ten_percent_discount(): asse...
A closure is a function that remembers the variables from the place where it was created, even after that outer function has returned. Closures are behind callbacks, React hooks, module patterns and much more. Lexical scope const greeting = 'Hello'; function o...
Ruff is a Python linter and formatter written in Rust. It implements rules from Flake8 and many of its plugins, sorts imports like isort, and formats code in a Black-compatible style, typically in a fraction of a second. Install and run uv add --dev ruff uv ru...
Some events fire very often: typing, scrolling, resizing. Running expensive work (an API call, a layout calculation) on every event wastes resources and can make the page janky. Debounce: wait until things calm down Run the function only after the events have...
A list holds every item in memory. A generator produces items one at a time, on demand. For large files, streams or infinite sequences, that's the difference between working and running out of memory. yield def read_lines(path): with open(path) as f: for line...
Users navigate away, type a new search or close a dialog while a request is still running. AbortController lets you cancel that work instead of letting it finish uselessly or, worse, overwrite newer results. Cancel a fetch const controller = new AbortControlle...
For decades, CPython's Global Interpreter Lock (GIL) allowed only one thread to run Python bytecode at a time. Threads helped with I/O, but not with CPU-heavy work. Free-threaded builds of Python remove the GIL. The timeline Python 3.13 introduced an experimen...
