Intermediate code explainers

go

package config
 
import (
	"bufio"

Parsing INI files in Go

parsing state-machine error-handling

Intermediate 7 steps

typescript

import { Component, computed, input, model, signal } from '@angular/core';
import { FormsModule } from '@angular/forms';
 
interface Product {

Reactive filtering with Angular signals

signals computed two-way-binding

Intermediate 9 steps

javascript

import { after } from "next/server";
import { NextResponse } from "next/server";
import { z } from "zod";
import { resend } from "@/lib/resend";

Deferring work with after() in Next.js

validation background-tasks route-handlers

Intermediate 8 steps

python

import os
from uuid import uuid4
 
from flask import Blueprint, current_app, jsonify, request, url_for

How a Flask image upload endpoint works

file-upload validation image-processing

Intermediate 9 steps

rust

use axum::{
    async_trait,
    extract::FromRequestParts,
    http::{header::HeaderName, request::Parts, StatusCode},

A custom tenant extractor in Axum

extractors middleware error-handling

Intermediate 7 steps

java

public class Views {
    public interface Public {}
    public interface Internal extends Public {}
}

Filtering JSON fields with @JsonView in Spring

serialization json-view access-control

Intermediate 6 steps

ruby

class ChatChannel < ApplicationCable::Channel
  periodically :sweep_stale_typists, every: 3.seconds
 
  def subscribed

How a typing indicator works in Rails ActionCable

websockets presence cache-expiry

Intermediate 9 steps

php

<?php
 
namespace App\Http\Controllers;

How a soft-delete restore endpoint works in Laravel

soft-deletes authorization single-action-controller

Intermediate 5 steps

go

package logtail
 
import (
	"bufio"

How a tail -f follower works in Go

io context channels

Intermediate 10 steps

typescript

type QueryValue = string | number | boolean | null | undefined;
type QueryInput = QueryValue | QueryValue[] | { [key: string]: QueryInput };
 
function buildQueryString(params: Record<string, QueryInput>): string {

Building nested query strings recursively

recursion url-encoding serialization

Intermediate 8 steps

python

from flask import g, session
 
from .extensions import cache
from .models import User

Injecting the current user in Flask templates

context-processor caching authentication

Intermediate 6 steps

rust

#[derive(Debug, Deserialize)]
pub struct SearchParams {
    #[serde(default)]
    q: String,

Building a safe search query in Axum

query parameters deserialization sql-building

Intermediate 10 steps

java

import java.util.Arrays;
import java.util.List;
 
public final class LatencyStats {

Computing latency percentiles in Java

percentiles interpolation immutability

Intermediate 9 steps

ruby

class Author < ApplicationRecord
  has_many :posts
 
  scope :with_post_stats, -> {

Aggregating post stats in a Rails scope

scopes sql-aggregation left-join

Intermediate 8 steps

php

<?php
 
namespace App\Models;

Auto-pruning old records with Laravel's Prunable

pruning eloquent cleanup

Intermediate 5 steps

typescript

type RGB = { r: number; g: number; b: number };
 
function parseHex(hex: string): RGB {
  const normalized = hex.replace(/^#/, "").trim();

Lightening and darkening hex colors in TypeScript

bitwise color-manipulation parsing

Intermediate 9 steps

java

@Configuration
public class WebConfig {
 
    @Bean

HTTP caching with ETags in Spring

http-caching etag servlet-filters

Intermediate 6 steps

ruby

require "securerandom"
require "time"
 
class ICalEvent

Building an iCalendar file in Ruby

serialization string-formatting file-formats

Intermediate 10 steps