Advanced code explainers

rust

use std::sync::{mpsc, Arc, Mutex};
use std::thread;
use std::time::Duration;

Building a thread pool in Rust

concurrency channels thread-pool

Advanced 9 steps

typescript

import { Pipe, PipeTransform, ChangeDetectorRef, NgZone, OnDestroy } from '@angular/core';
 
@Pipe({
  name: 'timeAgo',

A self-refreshing timeAgo pipe in Angular

impure-pipe change-detection timers

Advanced 10 steps

python

import csv
import io
from datetime import date

Streaming a CSV export in FastAPI

streaming async-generators csv

Advanced 8 steps

rust

use axum::{
    response::sse::{Event, KeepAlive, Sse},
    routing::get,
    Router,

Streaming live price ticks with SSE in Axum

server-sent-events broadcast-channel streaming

Advanced 8 steps

java

@Entity
@Table(name = "accounts")
public class Account {

Optimistic locking with @Version in Spring

optimistic-locking jpa concurrency

Advanced 7 steps

python

from django.db.models import Sum, Count, F, DecimalField
from django.db.models.functions import TruncMonth, Coalesce
 
from .models import Order

Build a monthly revenue report in Django

aggregation orm group-by

Advanced 7 steps

typescript

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Observable, throwError, timer } from 'rxjs';
import { mergeMap, retryWhen } from 'rxjs/operators';

Exponential backoff retries in Angular

retry exponential-backoff rxjs

Advanced 7 steps

python

from dataclasses import dataclass, fields, MISSING
from typing import get_type_hints, get_origin, get_args, Union

Type-checking dataclasses at runtime

dataclasses type-hints runtime-validation

Advanced 8 steps

ruby

class PaymentsController < ApplicationController
  before_action :require_idempotency_key
 
  def create

Idempotent payment creation in Rails

idempotency transactions race-conditions

Advanced 10 steps

javascript

import { useCallback, useEffect, useRef, useState } from 'react';
 
export function useInfiniteScroll(fetchPage) {
  const [items, setItems] = useState([]);

Building an infinite scroll hook in React

custom-hooks intersection-observer pagination

Advanced 6 steps

python

import os
import tempfile
from pathlib import Path
from typing import Union

How atomic file writes work in Python

atomicity filesystem durability

Advanced 7 steps

javascript

const fs = require('fs');
const path = require('path');
 
router.get('/downloads/:name', (req, res, next) => {

Streaming file downloads in Express

streaming backpressure file-download

Advanced 9 steps

java

@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
 
    @QueryHints(@QueryHint(name = HINT_FETCH_SIZE, value = "1000"))

Streaming large result sets in Spring Data JPA

streaming jpa memory-management

Advanced 6 steps

python

class Typed:
    """A data descriptor that enforces a type and optional validation."""
 
    def __init__(self, expected_type, validator=None):

Building a typed descriptor in Python

descriptors validation metaprogramming

Advanced 8 steps

javascript

// Sliding window maximum using a monotonic decreasing deque.
// Returns an array of the maximum value within each window of size k.
function maxSlidingWindow(nums, k) {
  const result = [];

Sliding window maximum with a deque

sliding-window monotonic-deque amortized-analysis

Advanced 7 steps

rust

use std::thread;
 
pub fn parallel_map_reduce<T, M, R, F, G, H>(
    data: &[T],

A parallel map-reduce with scoped threads

concurrency scoped-threads map-reduce

Advanced 8 steps

javascript

function throttle(fn, wait) {
  let lastCall = 0;
  let timeoutId = null;
  let lastArgs = null;

Building a leading-and-trailing throttle

closures rate-limiting timers

Advanced 6 steps

typescript

type Split<S extends string, D extends string> =
  S extends `${infer Head}${D}${infer Tail}`
    ? [Head, ...Split<Tail, D>]
    : [S];

Type-level string parsing in TypeScript

template literal types conditional types recursive types

Advanced 8 steps