A technology blog for developers, featuring programming tutorials, AI technologies, developer tools and emerging tech trends.https://blog.szkit99.com/enhttps://blog.szkit99.com/en/articles/go-build-a-cli-tool/https://blog.szkit99.com/en/articles/go-build-a-cli-tool/A line-counting CLI from scratch: flag parsing, reading files or stdin, bufio scanning with a raised buffer, exit codes, subcommands, and version injection with ldflags.Tue, 03 Nov 2026 00:00:00 GMTGoCLIToolinghttps://blog.szkit99.com/en/articles/go-build-an-http-service/https://blog.szkit99.com/en/articles/go-build-an-http-service/A JSON API with only net/http: method-based routing, request decoding and validation, a single error shape, request ID and logging middleware, timeouts, graceful shutdown, httptest.Tue, 03 Nov 2026 00:00:00 GMTGoHTTPServershttps://blog.szkit99.com/en/articles/go-context-and-cancellation/https://blog.szkit99.com/en/articles/go-context-and-cancellation/What context is for: Background versus TODO, WithCancel/WithTimeout/WithDeadline, ctx as the first parameter, select on Done, leaks, why it must not live in a struct.Tue, 03 Nov 2026 00:00:00 GMTGoContextConcurrencyhttps://blog.szkit99.com/en/articles/go-control-flow/https://blog.szkit99.com/en/articles/go-control-flow/Why Go has exactly one loop, how the if initialiser keeps variables scoped, what switch does differently, and how range behaves over slices, maps and strings.Tue, 03 Nov 2026 00:00:00 GMTGoControl FlowRangehttps://blog.szkit99.com/en/articles/go-functions-and-errors/https://blog.szkit99.com/en/articles/go-functions-and-errors/Multiple and named results, the error interface, wrapping with %w and inspecting with errors.Is and errors.As, plus where defer, panic and recover belong.Tue, 03 Nov 2026 00:00:00 GMTGoFunctionsErrorshttps://blog.szkit99.com/en/articles/go-generics-intro/https://blog.szkit99.com/en/articles/go-generics-intro/Type parameters and constraints: any and comparable, custom constraints with ~, Map and Filter helpers, generic types, type inference, and when not to use generics.Tue, 03 Nov 2026 00:00:00 GMTGoGenericsType Parametershttps://blog.szkit99.com/en/articles/go-goroutines-and-channels/https://blog.szkit99.com/en/articles/go-goroutines-and-channels/The concurrency primitives, used correctly: go with WaitGroup, buffered versus unbuffered channels, close and range rules, select and timeouts, worker pools, mutex versus channels.Tue, 03 Nov 2026 00:00:00 GMTGoGoroutinesChannelshttps://blog.szkit99.com/en/articles/go-install-and-hello-world/https://blog.szkit99.com/en/articles/go-install-and-hello-world/Install Go 1.24, understand what GOPATH and module mode really mean, and get comfortable with go mod init, go run, go build, go fmt and go vet.Tue, 03 Nov 2026 00:00:00 GMTGoInstallationModuleshttps://blog.szkit99.com/en/articles/go-interfaces-and-composition/https://blog.szkit99.com/en/articles/go-interfaces-and-composition/Implicit interface satisfaction, why small interfaces travel further, type assertions and type switches, the nil-interface trap, and composition over inheritance.Tue, 03 Nov 2026 00:00:00 GMTGoInterfacesCompositionhttps://blog.szkit99.com/en/articles/go-maps-and-structs/https://blog.szkit99.com/en/articles/go-maps-and-structs/Declaring and populating maps, the comma-ok idiom, why nil maps panic on write, plus struct literals, exported fields, JSON tags and embedding.Tue, 03 Nov 2026 00:00:00 GMTGoMapsStructshttps://blog.szkit99.com/en/articles/go-packages-and-modules/https://blog.szkit99.com/en/articles/go-packages-and-modules/How modules, packages and directories fit together: go.mod and go.sum, internal packages, exported identifiers, go get and go mod tidy, MVS, replace, vendor and cycles.Tue, 03 Nov 2026 00:00:00 GMTGoModulesPackageshttps://blog.szkit99.com/en/articles/go-pointers-and-methods/https://blog.szkit99.com/en/articles/go-pointers-and-methods/Address-of and dereference, new versus composite literals, value and pointer receivers, method sets and interface satisfaction, plus when a pointer is worth it.Tue, 03 Nov 2026 00:00:00 GMTGoPointersMethodshttps://blog.szkit99.com/en/articles/go-profiling-with-pprof/https://blog.szkit99.com/en/articles/go-profiling-with-pprof/Capture CPU and heap profiles from benchmarks or a live server, read top, list and flame graphs, compare allocations, and keep /debug/pprof off the public internet.Tue, 03 Nov 2026 00:00:00 GMTGoPerformancepprofhttps://blog.szkit99.com/en/articles/go-slices-vs-arrays/https://blog.szkit99.com/en/articles/go-slices-vs-arrays/Arrays carry their length in the type and copy on assignment; slices are small descriptors over shared memory. Length, capacity and append aliasing explained.Tue, 03 Nov 2026 00:00:00 GMTGoSlicesArrayshttps://blog.szkit99.com/en/articles/go-testing-and-benchmarks/https://blog.szkit99.com/en/articles/go-testing-and-benchmarks/Table-driven tests with the testing package: subtests, t.Helper and t.Cleanup, temp dirs, httptest, benchmarks with b.Loop, allocs/op, coverage and fuzzing.Tue, 03 Nov 2026 00:00:00 GMTGoTestingBenchmarkshttps://blog.szkit99.com/en/articles/go-variables-and-types/https://blog.szkit99.com/en/articles/go-variables-and-types/var versus :=, the zero-value design that removes uninitialised variables, constants and iota, and the boundaries between string, byte and rune.Tue, 03 Nov 2026 00:00:00 GMTGoVariablesTypeshttps://blog.szkit99.com/en/articles/js-array-methods/https://blog.szkit99.com/en/articles/js-array-methods/Split the array API into methods that mutate and methods that return a new array, then use map, filter, reduce, find and some correctly, including sort's string default.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptArraysHigher-Order Functionshttps://blog.szkit99.com/en/articles/js-async-and-promises/https://blog.szkit99.com/en/articles/js-async-and-promises/Why 1 4 3 2 is the correct order, promise states and chaining, async/await error handling, serial versus parallel work, the four combinators, and concurrency limits.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptAsyncPromiseshttps://blog.szkit99.com/en/articles/js-browser-app-without-framework/https://blog.szkit99.com/en/articles/js-browser-app-without-framework/A reading list in plain JavaScript: one state object plus a render function, event delegation, localStorage with validation and migration, form errors, and keyboard access.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptDOMWeb Apphttps://blog.szkit99.com/en/articles/js-cli-tool-with-node/https://blog.szkit99.com/en/articles/js-cli-tool-with-node/Build linkscan: parse arguments with parseArgs, walk Markdown files, probe external links with bounded concurrency, print machine-readable output, and return real exit codes.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptCLINode.jshttps://blog.szkit99.com/en/articles/js-conditionals-and-loops/https://blog.szkit99.com/en/articles/js-conditionals-and-loops/Pick between if, switch, for, for...of and while with intent, and avoid the iteration bugs: fall-through cases, for...in on arrays, and break inside forEach.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptControl FlowLoopshttps://blog.szkit99.com/en/articles/js-dom-and-events/https://blog.szkit99.com/en/articles/js-dom-and-events/Selecting and creating nodes, batching updates, capture and bubble, event delegation, listener cleanup with AbortSignal, form handling, and the XSS risk in innerHTML.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptDOMEventshttps://blog.szkit99.com/en/articles/js-error-handling/https://blog.szkit99.com/en/articles/js-error-handling/What an Error carries, when to throw, how try/catch/finally runs, custom error classes with instanceof, the cause option, and why async errors escape try/catch.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptError Handlinghttps://blog.szkit99.com/en/articles/js-fetch-and-http/https://blog.szkit99.com/en/articles/js-fetch-and-http/fetch does not reject on 404, a body can be read once, timeouts need AbortSignal, retries need backoff, and browsers add CORS on top of all of it.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptfetchHTTPhttps://blog.szkit99.com/en/articles/js-functions-and-scope/https://blog.szkit99.com/en/articles/js-functions-and-scope/Compare declarations, expressions and arrow functions, use default and rest parameters, and understand scope chains, closures, and the classic var-in-a-loop trap.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptFunctionsClosureshttps://blog.szkit99.com/en/articles/js-modules-esm-and-cjs/https://blog.szkit99.com/en/articles/js-modules-esm-and-cjs/Named and default exports, live bindings, dynamic import, the CommonJS snapshot trap, interop rules in Node, the exports map, and how to break a cycle.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptModulesESMhttps://blog.szkit99.com/en/articles/js-objects-and-destructuring/https://blog.szkit99.com/en/articles/js-objects-and-destructuring/Object literals, property access and iteration, destructuring with renames and defaults, and why spreading gives you a shallow copy that still shares nested objects.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptObjectsDestructuringhttps://blog.szkit99.com/en/articles/js-operators-and-type-coercion/https://blog.szkit99.com/en/articles/js-operators-and-type-coercion/Why == surprises you, which eight values are falsy, how + and - coerce differently, and when to reach for ??, ?. and Number.isNaN().Tue, 03 Nov 2026 00:00:00 GMTJavaScriptOperatorsType Coercionhttps://blog.szkit99.com/en/articles/js-strings-and-template-literals/https://blog.szkit99.com/en/articles/js-strings-and-template-literals/Template literal interpolation, string immutability, UTF-16 length surprises, slice versus substring, and why replace() only changes the first match.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptStringsTemplate Literalshttps://blog.szkit99.com/en/articles/js-testing-with-vitest/https://blog.szkit99.com/en/articles/js-testing-with-vitest/Set up Vitest, pick the right assertion, test async code with fake timers, replace dependencies with vi.fn and vi.mock, and enforce coverage in CI.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptTestingVitesthttps://blog.szkit99.com/en/articles/js-tooling-and-package-management/https://blog.szkit99.com/en/articles/js-tooling-and-package-management/package.json fields that matter, lockfiles and npm ci, script conventions, Vite dev versus build, why VITE_ variables are public, and ESLint versus Prettier.Tue, 03 Nov 2026 00:00:00 GMTJavaScriptnpmVitehttps://blog.szkit99.com/en/articles/js-variables-and-data-types/https://blog.szkit99.com/en/articles/js-variables-and-data-types/How var, let and const differ in scope, hoisting and rebinding, what the temporal dead zone protects you from, and why typeof null returns "object".Tue, 03 Nov 2026 00:00:00 GMTJavaScriptVariablesData Typeshttps://blog.szkit99.com/en/articles/php-build-a-todo-app/https://blog.szkit99.com/en/articles/php-build-a-todo-app/A complete PHP project: SQLite schema, add/toggle/delete over POST, CSRF tokens, Post/Redirect/Get with flash messages, escaped views, and a pre-deploy checklist.Tue, 03 Nov 2026 00:00:00 GMTPHPPDOProjecthttps://blog.szkit99.com/en/articles/php-composer-and-namespaces/https://blog.szkit99.com/en/articles/php-composer-and-namespaces/Dependency management and PSR-4 autoloading: composer.json structure, namespace mapping, version constraints, the lock file, scripts and autoloader optimisation.Tue, 03 Nov 2026 00:00:00 GMTPHPComposerNamespaceshttps://blog.szkit99.com/en/articles/php-conditionals-and-loops/https://blog.szkit99.com/en/articles/php-conditionals-and-loops/if versus match versus switch, when to use for, foreach and while, break/continue with nesting levels, and the alternative colon syntax that keeps HTML templates readable.Tue, 03 Nov 2026 00:00:00 GMTPHPControlFlowLoopshttps://blog.szkit99.com/en/articles/php-debugging-and-logging/https://blog.szkit99.com/en/articles/php-debugging-and-logging/Two error configurations, custom handlers for errors and exceptions, JSON logs with request IDs, Xdebug breakpoints, and a triage order for the white screen.Tue, 03 Nov 2026 00:00:00 GMTPHPDebuggingLogginghttps://blog.szkit99.com/en/articles/php-error-handling/https://blog.szkit99.com/en/articles/php-error-handling/How PHP separates errors from exceptions, the Throwable hierarchy, try/catch/finally, which exception class to throw, JSON_THROW_ON_ERROR, a global handler, and production error settings.Tue, 03 Nov 2026 00:00:00 GMTPHPExceptionsErrorshttps://blog.szkit99.com/en/articles/php-file-io/https://blog.szkit99.com/en/articles/php-file-io/file_get_contents and file_put_contents for small files, fgets streaming for large ones, file locking for concurrent writes, directory iteration with SPL, and why paths must start from __DIR__.Tue, 03 Nov 2026 00:00:00 GMTPHPFilesIOhttps://blog.szkit99.com/en/articles/php-forms-and-request-handling/https://blog.szkit99.com/en/articles/php-forms-and-request-handling/Work with $_GET and $_POST safely: choose the right method, validate with filter_var, escape output with htmlspecialchars, and follow Post/Redirect/Get to stop duplicate submissions.Tue, 03 Nov 2026 00:00:00 GMTPHPFormsSecurityhttps://blog.szkit99.com/en/articles/php-functions-and-scope/https://blog.szkit99.com/en/articles/php-functions-and-scope/Declare parameter and return types, use defaults and named arguments, understand pass-by-value versus reference and object handles, plus closures, arrow functions and static locals.Tue, 03 Nov 2026 00:00:00 GMTPHPFunctionsTypeshttps://blog.szkit99.com/en/articles/php-oop-and-types/https://blog.szkit99.com/en/articles/php-oop-and-types/Constructor promotion, readonly properties, backed enums, interfaces versus abstract classes, traits, union and nullable types, and why strict_types comes first.Tue, 03 Nov 2026 00:00:00 GMTPHPOOPTypeshttps://blog.szkit99.com/en/articles/php-pdo-and-prepared-statements/https://blog.szkit99.com/en/articles/php-pdo-and-prepared-statements/Safe database access with PDO: DSN and connection options, exception mode, named and positional parameters, transactions, and where placeholders stop working.Tue, 03 Nov 2026 00:00:00 GMTPHPPDOSQLhttps://blog.szkit99.com/en/articles/php-rest-api-with-pdo/https://blog.szkit99.com/en/articles/php-rest-api-with-pdo/A minimal REST API without a framework: method dispatch, one JSON error shape, input validation, pagination and sort whitelists, status codes, and curl checks.Tue, 03 Nov 2026 00:00:00 GMTPHPRESTAPIhttps://blog.szkit99.com/en/articles/php-sessions-and-cookies/https://blog.szkit99.com/en/articles/php-sessions-and-cookies/Start and use sessions, destroy them properly, regenerate the ID on login to prevent fixation, set cookies with secure, httponly and samesite, and never trust cookie contents.Tue, 03 Nov 2026 00:00:00 GMTPHPSessionCookieshttps://blog.szkit99.com/en/articles/php-strings-and-arrays/https://blog.szkit99.com/en/articles/php-strings-and-arrays/Indexed and associative arrays, how foreach really iterates, array_map/filter/reduce, the difference between + and array_merge, and the string functions you need — including mb_* for UTF-8.Tue, 03 Nov 2026 00:00:00 GMTPHPStringsArrayshttps://blog.szkit99.com/en/articles/php-templates-and-layouts/https://blog.szkit99.com/en/articles/php-templates-and-layouts/Split querying from output with one small render function: layouts, partials, htmlspecialchars-based escaping, alternative syntax, and what views must never do.Tue, 03 Nov 2026 00:00:00 GMTPHPTemplatesViewshttps://blog.szkit99.com/en/articles/php-unit-testing-with-phpunit/https://blog.szkit99.com/en/articles/php-unit-testing-with-phpunit/Install PHPUnit 11 with Composer, choose assertions that actually fail, use data providers and test doubles, test PDO code on SQLite, and run coverage in CI.Tue, 03 Nov 2026 00:00:00 GMTPHPTestingPHPUnithttps://blog.szkit99.com/en/articles/php-variables-and-data-types/https://blog.szkit99.com/en/articles/php-variables-and-data-types/Variable syntax and scope, the scalar types, strings and arrays, why loose comparison bites, what declare(strict_types=1) actually changes, and the falsy values that surprise newcomers.Tue, 03 Nov 2026 00:00:00 GMTPHPVariablesTypeshttps://blog.szkit99.com/en/articles/python-classes-and-oop/https://blog.szkit99.com/en/articles/python-classes-and-oop/Define classes, tell instance and class attributes apart, use @property, @classmethod and inheritance with super(), and implement __repr__ and __eq__ correctly.Tue, 03 Nov 2026 00:00:00 GMTPythonOOPhttps://blog.szkit99.com/en/articles/python-cli-argparse-and-project-structure/https://blog.szkit99.com/en/articles/python-cli-argparse-and-project-structure/Build a CLI with argparse: positional and optional arguments, types, choices, custom validators and subcommands, then package it with src layout, pyproject.toml and correct exit codes.Tue, 03 Nov 2026 00:00:00 GMTPythonCLIargparsehttps://blog.szkit99.com/en/articles/python-comprehensions-and-iteration/https://blog.szkit99.com/en/articles/python-comprehensions-and-iteration/List, dict and set comprehensions, generator expressions, and the standard library helpers — enumerate, zip, sorted, itertools — that replace most manual loops.Tue, 03 Nov 2026 00:00:00 GMTPythonIterationitertoolshttps://blog.szkit99.com/en/articles/python-conditionals-and-loops/https://blog.szkit99.com/en/articles/python-conditionals-and-loops/How truthiness works in Python, when to use for versus while, the rarely used loop else clause, and the iteration mistakes that produce wrong results.Tue, 03 Nov 2026 00:00:00 GMTPythonControl Flowhttps://blog.szkit99.com/en/articles/python-data-cleaning-csv-json/https://blog.szkit99.com/en/articles/python-data-cleaning-csv-json/A complete, runnable script: read a messy CSV with csv.DictReader, validate and convert each row, count skipped rows by reason, aggregate with collections, and write a JSON report.Tue, 03 Nov 2026 00:00:00 GMTPythonCSVJSONDataProcessinghttps://blog.szkit99.com/en/articles/python-dataclasses-and-type-hints/https://blog.szkit99.com/en/articles/python-dataclasses-and-type-hints/Annotate your code so editors and mypy catch mistakes before runtime, then let @dataclass generate __init__, __repr__ and __eq__ — with default_factory, frozen and slots.Tue, 03 Nov 2026 00:00:00 GMTPythonType Hintsdataclasseshttps://blog.szkit99.com/en/articles/python-error-handling/https://blog.szkit99.com/en/articles/python-error-handling/How try/except/else/finally actually runs, which exceptions to catch, keeping context with raise from, designing custom error hierarchies, and the anti-patterns that hide bugs.Tue, 03 Nov 2026 00:00:00 GMTPythonExceptionshttps://blog.szkit99.com/en/articles/python-file-io-and-paths/https://blog.szkit99.com/en/articles/python-file-io-and-paths/Open files safely with with, stream large files line by line, build paths with pathlib, and handle JSON, CSV, and encodings without the usual surprises.Tue, 03 Nov 2026 00:00:00 GMTPythonFile I/OJSONhttps://blog.szkit99.com/en/articles/python-functions-and-arguments/https://blog.szkit99.com/en/articles/python-functions-and-arguments/Define functions, mix positional and keyword arguments, avoid the mutable default trap, collect extra arguments with *args and **kwargs, and understand scope rules.Tue, 03 Nov 2026 00:00:00 GMTPythonFunctionshttps://blog.szkit99.com/en/articles/python-iterators-and-generators/https://blog.szkit99.com/en/articles/python-iterators-and-generators/Separate iterables from iterators, trace exactly how yield suspends a function, stream a large file through a generator pipeline, and know when yield from, send and close are worth the complexity.Tue, 03 Nov 2026 00:00:00 GMTPythonGeneratorIteratorhttps://blog.szkit99.com/en/articles/python-lists-and-dicts/https://blog.szkit99.com/en/articles/python-lists-and-dicts/The list and dict operations you reach for daily: slicing, iteration, shallow versus deep copies, get versus indexing, and grouping with setdefault.Tue, 03 Nov 2026 00:00:00 GMTPythonListsDictshttps://blog.szkit99.com/en/articles/python-modules-packages-and-venv/https://blog.szkit99.com/en/articles/python-modules-packages-and-venv/How imports resolve, absolute versus relative imports, the __main__ guard, and isolating dependencies per project with venv, pip and pyproject.toml.Tue, 03 Nov 2026 00:00:00 GMTPythonModulesvenvhttps://blog.szkit99.com/en/articles/python-regex-basics/https://blog.szkit99.com/en/articles/python-regex-basics/How search, match, findall and sub actually differ, the metacharacters you need, greedy versus lazy quantifiers, named groups, compile flags, and the failure modes that make regexes fragile.Tue, 03 Nov 2026 00:00:00 GMTPythonRegexhttps://blog.szkit99.com/en/articles/python-standard-library-essentials/https://blog.szkit99.com/en/articles/python-standard-library-essentials/The standard library modules worth knowing by heart: datetime arithmetic and time zones, Counter, defaultdict and deque, json round-trips, plus os.getenv, subprocess and secrets.Tue, 03 Nov 2026 00:00:00 GMTPythonStandardLibraryhttps://blog.szkit99.com/en/articles/python-strings-and-formatting/https://blog.szkit99.com/en/articles/python-strings-and-formatting/Create and inspect strings, use the methods you actually reach for, format output with f-strings, and keep str and bytes straight at the encoding boundary.Tue, 03 Nov 2026 00:00:00 GMTPythonStringshttps://blog.szkit99.com/en/articles/python-testing-with-pytest/https://blog.szkit99.com/en/articles/python-testing-with-pytest/Write your first pytest test, then use plain asserts, pytest.raises, parametrize, fixtures and tmp_path — plus how to organise tests and the anti-patterns that make a suite untrustworthy.Tue, 03 Nov 2026 00:00:00 GMTPythonTestingpytesthttps://blog.szkit99.com/en/articles/python-tuples-and-sets/https://blog.szkit99.com/en/articles/python-tuples-and-sets/When a tuple beats a list, how packing and unpacking work, what immutability actually prevents, and why sets give O(1) membership tests.Tue, 03 Nov 2026 00:00:00 GMTPythonData Structureshttps://blog.szkit99.com/en/articles/what-is-an-ai-agent/https://blog.szkit99.com/en/articles/what-is-an-ai-agent/Break down the observe-decide-act loop behind AI agents, how they differ from chat and scripts, and when you should not use one.Mon, 02 Nov 2026 00:00:00 GMTAIAgentLLMhttps://blog.szkit99.com/en/articles/python-variables-and-data-types/https://blog.szkit99.com/en/articles/python-variables-and-data-types/How Python variable binding actually works, the built-in types you use daily, and why mutable vs immutable changes how bugs show up.Mon, 02 Nov 2026 00:00:00 GMTPythonData Types