Code Explainers

Code explainers tagged #error-handling

javascript 
export function cloneState(state) {
  if (typeof structuredClone !== "function") {
    throw new Error("structuredClone is not available in this runtime");
  }

Deep cloning with structuredClone

deep-copy error-handling immutability
Intermediate 7 steps
rust 
use serde::Deserialize;
use serde_json::Value;
use std::collections::HashMap;
 

Modeling nested JSON with serde in Rust

deserialization json struct-mapping
Intermediate 9 steps
python 
import threading
import logging
 
logger = logging.getLogger(__name__)

A self-rescheduling periodic task in Python

threading scheduling concurrency
Intermediate 6 steps
go 
func UploadFiles(c *gin.Context) {
	form, err := c.MultipartForm()
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid multipart form"})

Handling multi-file uploads in Gin

file-upload multipart validation
Intermediate 8 steps
ruby 
class PurgeStaleExportsJob < ApplicationJob
  queue_as :maintenance
 
  retry_on ActiveRecord::Deadlocked, wait: :polynomially_longer, attempts: 5

Purging stale exports with an Active Job in Rails

background-jobs batching error-handling
Intermediate 7 steps
python 
from fastapi import Depends, FastAPI, HTTPException
from sqlalchemy import create_engine
from sqlalchemy.orm import Session, sessionmaker
 

Wiring SQLAlchemy sessions into FastAPI

dependency-injection orm sessions
Intermediate 7 steps
javascript 
const { validationResult, matchedData } = require('express-validator');
 
function validate(schema) {
  const runners = schema.map((rule) => rule.run.bind(rule));

A reusable validation middleware in Express

middleware validation higher-order-functions
Intermediate 8 steps
go 
func RecoveryHandler(logger *zap.Logger) gin.HandlerFunc {
	return gin.CustomRecovery(func(c *gin.Context, recovered any) {
		var brokenPipe bool
		if ne, ok := recovered.(*net.OpError); ok {

A panic-recovery middleware in Gin

middleware panic-recovery structured-logging
Intermediate 6 steps
javascript 
const STORAGE_KEY = "app_state";
const CURRENT_VERSION = 3;
 
const migrations = {

Versioned state migrations in localStorage

migrations persistence versioning
Intermediate 9 steps
php 
<?php
 
namespace App\Http\Controllers;
 

Verifying Stripe webhooks in Laravel

webhooks signature-verification event-dispatch
Intermediate 8 steps
javascript 
const asyncHandler = (fn) => (req, res, next) => {
  Promise.resolve(fn(req, res, next)).catch(next);
};
 

Async error handling in Express routes

async-await error-handling middleware
Intermediate 7 steps
rust 
use axum::{
    extract::{Path, State},
    http::StatusCode,
    routing::get,

Building a JSON user API in Axum

routing shared-state json-serialization
Intermediate 8 steps
rust 
use axum::{
    body::Bytes,
    extract::State,
    http::StatusCode,

Handling raw byte uploads in Axum

extractors shared-state request-limits
Intermediate 7 steps
javascript 
const RETRIABLE_STATUS = new Set([408, 429, 500, 502, 503, 504]);
 
function sleep(ms, signal) {
  return new Promise((resolve, reject) => {

Retrying fetch with exponential backoff

retry exponential-backoff abort-signal
Advanced 8 steps
rust 
use axum::{
    extract::{Query, State},
    http::StatusCode,
    Json,

Paginated, filtered product listing in Axum

pagination query-parameters sql-filtering
Intermediate 8 steps
php 
<?php
 
namespace App\Support;
 

Retry with exponential backoff in PHP

retry exponential-backoff error-handling
Intermediate 7 steps
typescript 
import { inject } from '@angular/core';
import { ResolveFn, Router, ActivatedRouteSnapshot } from '@angular/router';
import { catchError, of, EMPTY } from 'rxjs';
import { Article } from './models/article';

Prefetching route data with an Angular resolver

route-resolver dependency-injection rxjs
Intermediate 6 steps
python 
from itertools import islice
from typing import Iterable, Iterator, TypeVar
 
T = TypeVar("T")

Batching an iterable for bulk indexing

generators batching lazy-evaluation
Intermediate 7 steps