Programming Tutorials and Coding Guides - Page 20

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. …

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.

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 …

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.

Convert array to string in JavaScript with join, toString, String(), toLocaleString, JSON.stringify, reduce, or loops—with example output and common pitfalls (objects, BigInt, null/undefined).

Fix Error [ERR_HTTP_HEADERS_SENT] and cannot set headers after they are sent in Express/Node: double res.send, async races, middleware next(), error handlers, and res.headersSent—with tested client and log lines.

Use Node.appendChild in JavaScript to add or move elements. Includes append vs appendChild, DocumentFragment batching, insertBefore, cloneNode, and jsdom-tested console output.

Convert srt to text or srt to txt in JavaScript: regex to remove index and timestamp lines, line-skip variant, block split for multi-line cues, Node readFileSync/writeFileSync with utf8—no npm install fs. Includes …

Format dates in JavaScript with Intl.DateTimeFormat: locales, dateStyle and timeStyle, time zones, formatRange, formatToParts, and common TypeErrors. Includes tested sample output from Node.js (V8).

Coerce strings with Boolean() and !!, or parse canonical values like 'true'/'false'. Learn the difference and avoid common mistakes.

Call vs invoke and invoke vs call in JavaScript: both usually mean run a function. Clarify this binding, method calls vs free calls, Function.prototype.call naming, and library methods named invoke—with example console …

How to detect adblock in JavaScript: bait DOM patterns, getComputedStyle and offsetWidth checks, BlockAdBlock (blockadblock js) global guard, common API mistakes, limitations and false positives—with example branch logic …

Use clearTimeout (cleartimeout in search terms) to cancel one or many setTimeout timers. JavaScript has no built-in clear-all—track handles in a Set or array, including in Node.js. Includes Node-tested console output, …

Check if key exists in object JavaScript: Object.hasOwn, in, hasOwnProperty, Object.keys, getOwnPropertyNames, symbols, Reflect.ownKeys—with example console output and own vs inherited rules.

Check if array is empty in JavaScript with length, Array.isArray, optional chaining, and loop patterns—plus pitfalls (array-like objects, sparse arrays). Includes Node-tested console output.

Golang goroutine and golang goroutines: goroutine in golang with the go keyword, go goroutines and go routine spelling, minimal goroutine example, waiting with channels or sync.WaitGroup, and links to threads vs …

Deep guide to json.Unmarshal in Go: []byte and pointer rules, structs with tags, maps and float64 numbers, slices, nested JSON, any decoding, null, json.RawMessage, unknown fields vs Decoder.DisallowUnknownFields, …

Learn how to parse JSON in Go using encoding/json: JSON strings, files, HTTP bodies, structs, maps, nested data, json.Unmarshal, json.Decoder, and common errors.

Golang function vs method and go method vs function: golang function declaration syntax without a receiver, method golang syntax with value or pointer receiver, function vs method call style, golang methods vs functions …

Bash unshift: prepend to an array or positional parameters, bash shift array / bash array shift, shift vs unshift, and bash pop argument / remove last element. No built-in unshift—use assignment or set --.

Bash while loop timeout and while loop until a deadline: sleep in Linux/Bash, wall-clock end time with date or EPOCHSECONDS, counter + break, and GNU timeout around background jobs.

Linux convert tabs to spaces with expand; convert runs of spaces to tabs with unexpand; tab in bash with $'\t' and printf; unix shell scripts conversion for tab- vs space-delimited text and aligned columns.

Exponentiation in JavaScript with the ** power operator and Math.pow: numbers, BigInt, right-associativity, unary minus precedence, NaN ** 0, **= compound assignment, and when to prefer Math.pow on older engines. Each …

Linux login history: view and check login history, login logs, and Linux SSH login history via last, wtmp, auth.log or /var/log/secure, and journalctl. Optional script to summarize successful and failed SSH attempts.

Grep word after match, grep everything after match, grep characters after match, grep next line after match, and awk print after match on Linux (GNU grep -P with \K, -A, match/substr). Brief patterns for the word before …

Use find with sha256sum (or md5sum) to list identical files on Linux, group by hash, then delete duplicate copies interactively or after a dry-run—plus how “duplicate by name” differs from same content.

Bash patterns to remove an element from an array, drop the first item, dedupe (bash array remove duplicates), and subtract all values of one array from another using loops or an associative map.

Build a bash progress bar and bash loading bar in the terminal with carriage return redraws, reusable functions, multi-step jobs, plus pv for pipe byte counts and dialog for a gauge widget.

Bash counter patterns: C-style for loop counter, bash while loop counter, increment with (( )) and let, bash for count over a list, and a small script counter over files—plus links to deeper increment and loop guides.

Count how many times a word or substring appears in a file, count lines and words with wc, whole-word matches with grep -E, and build a frequency table with awk or sort/uniq.