Intermediate code explainers

go

package handler
 
import (
	"net/http"

Custom time validation in Gin

validation request-binding struct-tags

Intermediate 8 steps

python

from pathlib import Path
 
from django.contrib.auth.decorators import login_required
from django.http import FileResponse, Http404, HttpResponseForbidden

Serving files with access checks in Django

authorization http-caching file-serving

Intermediate 7 steps

rust

use once_cell::sync::Lazy;
use regex::Regex;
 
static LOG_LINE: Lazy<Regex> = Lazy::new(|| {

Parsing access logs with a lazy regex in Rust

regex lazy-initialization parsing

Intermediate 7 steps

javascript

import { useState, useRef, useCallback } from "react";
 
export function MultiSelect({ options, value, onChange, placeholder = "Select…" }) {
  const [open, setOpen] = useState(false);

Building a keyboard-accessible MultiSelect in React

controlled-component accessibility keyboard-navigation

Intermediate 10 steps

java

public final class NaturalOrderComparator implements Comparator<String> {
 
    public static final NaturalOrderComparator INSTANCE = new NaturalOrderComparator();

Natural-order string sorting in Java

comparator natural-sort string-parsing

Intermediate 9 steps

go

package middleware
 
import (
	"net/http"

Localized validation errors in Gin

middleware internationalization validation

Intermediate 8 steps

php

<?php
 
namespace App\Http\Controllers;

Email confirmation with signed URLs in Laravel

signed-urls email-verification middleware

Intermediate 6 steps

typescript

import { Component, computed, signal } from '@angular/core';
import { CdkTableModule } from '@angular/cdk/table';
import { CdkScrollableModule } from '@angular/cdk/scrolling';

Paginating a CDK table with Angular signals

signals computed-state pagination

Intermediate 9 steps

ruby

require "csv"
 
class CsvExporter
  def initialize(records, columns: nil)

Turning records into CSV in Ruby

csv data-export serialization

Intermediate 7 steps

java

package com.example.validation;
 
import java.util.List;
import java.util.stream.Collectors;

Validating JSON payloads against a schema in Java

json-schema validation recursion

Intermediate 8 steps

rust

use std::collections::HashMap;
 
fn decode_component(input: &str) -> String {
    let bytes = input.as_bytes();

Parsing a URL query string in Rust

url-encoding byte-parsing iterators

Intermediate 8 steps

go

func ListProducts(c *gin.Context) {
	allowed := map[string]string{
		"category": "category",
		"brand":    "brand",

Safe query filtering in a Gin handler

input-validation whitelisting query-building

Intermediate 7 steps

typescript

type Semver = {
  major: number;
  minor: number;
  patch: number;

Parsing and comparing semver strings in TypeScript

parsing regular-expressions comparison

Intermediate 9 steps

javascript

function formatPhoneNumber(value) {
  const digits = value.replace(/\D/g, '').slice(0, 10);
  const parts = [];

Building a live phone number input mask

input-masking regex dom-events

Intermediate 7 steps

python

from flask import Blueprint, jsonify
from marshmallow import Schema, fields, validate, EXCLUDE
from webargs.flaskparser import use_args

Validating query params in Flask with webargs

validation schema query-building

Intermediate 10 steps

java

public URI buildSearchUri(String query, int page, int size, List<String> tags) {
    UriComponentsBuilder builder = UriComponentsBuilder
            .fromUriString("https://api.example.com")
            .path("/v2/products/search")

Building URIs safely with UriComponentsBuilder in Spring

url-building builder-pattern encoding

Intermediate 5 steps

rust

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FileKind {
    Png,
    Jpeg,

Detecting file types by magic bytes in Rust

pattern-matching byte-slices lookup-table

Intermediate 7 steps

go

func (h *ExportHandler) BulkExport(c *gin.Context) {
	projectID := c.Param("projectID")
 
	reports, err := h.reports.ListByProject(c.Request.Context(), projectID)

Streaming a ZIP download in Gin

streaming zip-archive http-headers

Intermediate 8 steps