JavaScript Variable Hoisting: var, let, const and TDZ
Hoisting makes every declaration exist from the start of its scope. var reads as undefined, let, const and class throw in the temporal dead zone, and function declarations work anywhere.
TypeScript is a popular open-source programming language developed and maintained by Microsoft. It is a statically typed superset of JavaScript that adds optional static typing and other features to help developers write more robust and maintainable code.
TypeScript compiles to plain JavaScript, making it compatible with all JavaScript environments and runtimes.
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Tutorials
Truthy and Falsy Values in JavaScript and TypeScript
JavaScript has eight falsy values; everything else, including “0”, [] and {}, is truthy. Learn where the conversion happens, how TypeScript narrows with it, and the bugs it causes.
Transpiler vs Compiler: The Difference, with TypeScript
A transpiler outputs source code at the same level as its input; a classic compiler outputs bytecode or machine code. Real javac, tsc and Node.js output shows the difference.
Mask Sensitive Data in Logs in JavaScript (JSON and pino)
Mask passwords, card numbers, emails and tokens before they reach a log file, using a JSON.stringify() replacer, a structuredClone() copy, regex for free text, toJSON(), and pino’s redact option.
Jasmine Unit Testing Tutorial with TypeScript Examples
Learn Jasmine unit testing with TypeScript on Node.js 22. Set up Jasmine 7, write specs with matchers and hooks, replace dependencies with spies, and test async code and timers.
How to Declare a JavaScript Global Variable With globalThis
A JavaScript global variable is a property of globalThis or a top-level declaration in a classic script. Learn how var, let and const behave in scripts, ES modules and CommonJS, why strict mode rejects implicit globals, and how to type globals in TypeScript.