Article URL: https://twitter.com/i/status/2071277885646868536 Comments URL: https://news.ycombinator.com/item?id=48719027 Points: 22 # Comments: 0
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JavaScript engines process code in two phases: a creation phase that registers all variable and function declarations, and an execution phase that runs code line by line. Variables declared with var are registered and initialized to undefined during creation, so accessing them early silently returns undefined rather than throwing an error. In contrast, let, const, and class declarations are registered but left uninitialized, placing them in a Temporal Dead Zone (TDZ) until their declaration line is reached — any early access throws a ReferenceError. Common bugs arise when a var variable is used before its assigned branch executes, or when a function declaration calls a const that is still in the TDZ. Developers can prevent most hoisting-related runtime errors by enabling lint rules such as no-var and no-use-before-define, which catch these issues at write time.
A developer spent nearly two days integrating Google OAuth into an Angular 20 app backed by IdentityServer8, documenting six critical mistakes along the way. The core issue was passing the Angular callback URL as the returnUrl to the challenge endpoint, when it should instead be the full OIDC authorize URL so IdentityServer can complete the code flow first. Additional problems included calling checkAuth() in multiple components simultaneously, causing a race condition that prevented token exchange. Misconfigurations like startCheckSession: true, an unset silentRenewUrl, and late OIDC config registration each triggered separate failures. The writeup serves as a practical troubleshooting guide for developers implementing external identity providers with IdentityServer and angular-auth-oidc-client.
Every time a JavaScript function runs, the engine creates an execution context containing scope, the value of 'this', and local variables, stacking these contexts in a call stack that follows LIFO order. Understanding this mechanism is critical for reading stack traces quickly and diagnosing errors like 'Maximum call stack size exceeded' under real traffic. Two common bugs tied directly to the call stack are uncontrolled recursion leading to stack overflow, and async code that silently drops stack traces when errors are not properly chained. Recursive functions without a base case or those traversing cyclic data structures can exhaust the call stack in production, and the recommended fix is converting to an iterative approach using an explicit stack with cycle detection. Since ES2022, JavaScript supports exception chaining via the 'cause' option when throwing errors, which preserves the original stack trace alongside business context for more useful production logs.
A freelance developer has released a collection of nine production-ready Telegram bots on GitHub, covering use cases such as AI assistance, appointment booking, crypto price alerts, job vacancy posting, and restaurant reservations. The project was born out of repetitive patterns the developer noticed across multiple client projects, prompting the creation of reusable templates. Built with Python 3.12 and aiogram 3.7, the bots use SQLite for data persistence and integrate free APIs including CoinGecko and HH.ru alongside Anthropic's Claude Haiku model for AI features. Each bot includes a subscription model with a free tier capped at 20 messages per day and an unlimited paid tier, along with an admin dashboard. All nine bots are freely available on GitHub with setup documentation, environment configuration examples, and dependency files.
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