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JavascriptA practical guide to regular expressions plus honest email validation — what a simple pattern catches, why RFC-compliant regexes are a trap, the ReDoS vulnerability lurking in clever patterns, and the only check that actually proves an address works.
JavascriptLexical scope decides which variables your code can see, based on where you wrote it. Understand the scope chain, closures, the temporal dead zone, and why `this` is the one thing that does not follow these rules.
JavascriptHow map, filter and reduce actually work, with real-world examples beyond doubling numbers — chaining, grouping with reduce, the empty-array crash, and when a plain for...of loop is the better choice.
JavascriptA complete comparison of var, let and const — scope, hoisting, the temporal dead zone, redeclaration, the global object, and why const does not mean immutable.
JavascriptRead the state of checkbox and radio groups without jQuery — counting selections, getting all values, select-all with indeterminate, mutually exclusive groups, and safely storing JSON in data attributes.
JavascriptPoll a server and update part of a page using fetch and recursive setTimeout — avoiding the overlapping requests setInterval causes, pausing on hidden tabs, backing off on errors, and knowing when to use SSE instead.
JavascriptGet a user's location and draw a route with the Google Maps JavaScript API — using the modern importLibrary loader, the API key and billing Google now requires, HTTPS-only geolocation, and honest handling of permission denial.
JavascriptPreview images before upload using FileReader or the faster URL.createObjectURL — with multi-file previews, drag and drop, client-side resizing, and the memory leak most tutorials leave in.
JavascriptHow to send browser notifications from a web application using the Notification API and Push API — permission handling that does not get you blocked, service worker notifications, and the iOS caveat most guides miss.
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