Dev.to•Feb 3, 2026, 4:17 AM
JavaScript's promises crash the VIP line ahead of zero-delay timeouts, starving the rest like a bad sprint planning meeting

JavaScript's promises crash the VIP line ahead of zero-delay timeouts, starving the rest like a bad sprint planning meeting

In the JavaScript ecosystem, a crucial distinction exists between microtasks and macrotasks, which affects the execution order of code. Timothy, a developer, was puzzled by the behavior of his code, which used `setTimeout` and `Promise.resolve()`. Margaret, an experienced developer, explained that the JavaScript engine maintains two queues: the Macrotask Queue for standard tasks like `setTimeout` and the Microtask Queue for high-priority tasks like Promises. The engine prioritizes microtasks over macrotasks, running all microtasks before moving to the macrotask queue. This can lead to starvation, where the browser freezes if too many microtasks are added. Margaret cautioned against abusing Promises, using them only for quick updates. This understanding is crucial for developers to write efficient and effective code, avoiding potential issues like starvation. By recognizing the distinction between microtasks and macrotasks, developers can better manage their code's execution order and prioritize tasks accordingly.

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