JavaScript addEventListener (DOM events, options, and examples)
JavaScript addEventListener on document, window, and elements: click, capture vs bubble, removeEventListener, once, passive, AbortSignal, delegation, and Node EventEmitter. DOM snippets use `{run=false}` (install jsdom …
JavaScript forEach vs for...in (arrays and objects)
Compare Array.prototype.forEach with for...in on objects and arrays, when for...of wins, and how to avoid enumerable-key bugs. Runnable Node snippets with short output notes.
Date/time out of range in JavaScript (and the PostgreSQL pq error)
Compare Date values in JavaScript to detect out-of-range times, and fix PostgreSQL pq: date/time field out of range from bad string formats.
JavaScript add to array: push, unshift, splice, concat, spread, length
How to add to arrays in JavaScript: javascript add to array, js add to array with push, unshift, splice, toSpliced, concat, spread, length holes, javascript add array to array, mutating vs new array, and links to append …
Add days to a date in JavaScript (UTC, local, DST caveats)
How to javascript add days to date and js date add days: getUTCDate/setUTCDate for UTC calendar days, getDate/setDate for local wall calendar, immutable copy pattern, getTime + 86400000 ms vs DST, negative days, and Intl …
insertBefore in JavaScript (DOM, null, nextSibling)
insertBefore javascript and js insert before: parent.insertBefore(newNode, referenceNode), referenceNode null for end append, firstChild text nodes, insert after via nextSibling, TypeError if second arg omitted. Examples …
Call a function every second in JavaScript (setInterval, cleanup)
JavaScript call function every second and every 5 seconds with setInterval and clearInterval, recursive setTimeout when work overlaps, setTimeout delays, async delay helper, timer cleanup, and Node/browser throttling …
JavaScript array range (Array.from, start/stop/step, loop)
Numeric ranges with Array.from, start/stop/step helpers, loops, and keys(). Snippets include short expected-output notes from Node runs.
How to copy an array in JavaScript (shallow vs deep)
JavaScript copy array: shallow copies with spread, slice, Array.from, concat, map, and filter; deep copies with structuredClone; JSON limitations; sparse-array caveats. Snippets include short expected-output notes from …
HashSet in JavaScript (`Set`, uniqueness, Map vs dedupe)
Hashset JavaScript and js hashset: use Set for unique values like a HashSet, add/has/delete, SameValueZero and NaN, object identity, dedupe arrays with spread, Map when you need keys. Section intros explain each pattern; …
Convert string to array JavaScript (split, Array.from, Unicode)
How to convert string to array in JavaScript: string to array javascript, javascript string to array, js string to array, convert string to array javascript with split, Array.from, spread, javascript string to char …
JavaScript copy to clipboard (navigator.clipboard.writeText, secure context)
Copy text to the clipboard with navigator.clipboard.writeText, secure contexts, NotAllowedError, readText, and why execCommand is legacy. Node uses a stub clipboard in examples so snippets run; browsers need HTTPS and …
JavaScript clone object (shallow spread, structuredClone, JSON)
Clone objects in JavaScript: shallow spread and Object.assign, for...in, Object.create + descriptors, JSON limits, structuredClone and DataCloneError, and circular refs. Runnable Node snippets with short output notes; …
JavaScript classes tutorial (constructor, methods, static, extends)
JavaScript classes: constructor, instance methods, getters, static methods, extends and super, public fields, and private # fields. Runnable Node snippets with short expected-output notes; links to ranges and cloning …
jQuery check if checkbox is checked (and JavaScript checked property)
Read checkbox state with HTMLInputElement.checked, jQuery .prop('checked') and .is(':checked'), why .attr('checked') misleads, and change events. Snippets use `{run=false}`—run in DevTools or with jsdom + jQuery 3.7; …
JavaScript check if undefined (typeof, ===, void 0, nullish)
Check undefined in JavaScript: typeof for undeclared names, === undefined for declared bindings, falsy vs undefined, == null, void 0, and nullish coalescing (??) for defaults. Runnable Node snippets with short output …
JavaScript check if string is number (Number.isFinite, isNaN, parseInt)
Validate numeric strings in JavaScript: whole-token checks with trim + Number.isFinite, global isNaN pitfalls, parseInt prefix behavior, integers, strict regex decimals, and digits-in-text vs fully numeric. Runnable Node …
JavaScript check if string contains space or whitespace (indexOf, RegExp, trim)
Check if a string contains spaces in JavaScript: literal U+0020 vs Unicode whitespace, indexOf and includes, RegExp \s, trim for ends-only emptiness, and NBSP (U+00A0) pitfalls. Runnable Node snippets with short …
JavaScript double exclamation mark (!!): boolean coercion
JavaScript double exclamation (!!) vs Boolean(): same boolean coercion to true/false, truthy and falsy lists, TypeScript idiom, and why [] is truthy. Runnable Node snippets with short output notes.
JavaScript double question mark (??): nullish coalescing
JavaScript double question mark (??) is nullish coalescing: defaults only for null or undefined, unlike ||. Covers chaining, mixing with ||/&& (parentheses), and examples where 0 and empty string must be preserved. …
Cannot use import statement outside a module
Fix SyntaxError cannot use import statement outside a module in Node.js, browsers, and AWS Lambda. Use type module, .mjs, script type=module, and avoid ERR_MODULE_NOT_FOUND confusion—with Node-tested output.
JavaScript findIndex: array findIndex and objects by property
findIndex javascript and js findIndex: predicate scan with Array.prototype.findIndex, return index or -1, optional thisArg, javascript find index of object in array by property, and how findIndex differs from find and …
Understanding Docker Vs Containerd
Container execution is handled by containerd. You can think of it as a container supervisor that handles container lifecycle operations.
Top 5 Best Practices for Containerized Deployments
Even though containers are valuable in the current software development trends, realizing containerized deployments in organizations is not easy. This article
7 tools to detect Memory Leaks with Examples
How to detect, capture and monitor memory leak in various applications such as C, C++ or in Linux process. use valgrind, core dump to capture leak information
How to limit CPU using cgroups (v2 and v1) on Linux
How to cap CPU with Linux cgroups: cgroup v2 cpu.max and cpu.stat, cgroup v1 cfs quota files, systemd CPUQuota and CPUWeight, shared limits with systemd slices, optional CPUQuotaPeriodSec, plus how this differs from …
How to Check Memory Usage per Process in Linux
Learn how to check memory usage by process in Linux with tested ps, top, pmap, /proc, smaps_rollup, statm, free, and pidstat examples. Understand RSS, VSZ, PSS, USS, shared memory, and how to find the top …
Linux memory limits in containers (cgroups, Docker, Kubernetes)
Learn how Linux enforces memory limits inside containers using cgroups, how cgroup v1 and v2 differ, why tools disagree, and how Docker and Kubernetes map limits to the kernel.
Debugging Kubernetes Operators: kubectl, Logs, and Webhook Failures
Learn how to debug Kubernetes Operators from the outside in: manager logs and flags, kubectl describe and events, stuck Terminating resources, validating and mutating webhooks (TLS, caBundle, cert-manager), conversion …
Compare strings in JavaScript: ===, localeCompare, and case-insensitive matches
JavaScript string compare and string equals with === vs ==, localeCompare and Intl.Collator for locale-aware sorting, case-insensitive patterns, trim and Unicode normalize—with example console output.