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Discover clear, example-based answers to real JavaScript challenges. From functions, arrays, and DOM manipulation to ES6+ syntax and async programming, every response is written to help you understand how and why things work. Whether you’re building interactive sites or learning core logic, these Q&As make JavaScript easier and more powerful.

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Why does my closure not retain the value of a loop variable in a setTimeout callback?

Asked on Friday, Jan 09, 2026

Closures in JavaScript capture variables by reference, not by value. In a loop, this can lead to unexpected behavior when using functions like "setTimeout". Here's how you can correctly capture the lo…

How do you handle caching and pagination differently when consuming REST vs GraphQL APIs in a JavaScript app?

Asked on Thursday, Jan 08, 2026

When consuming REST and GraphQL APIs in a JavaScript app, caching and pagination are handled differently due to their distinct architectures. REST typically uses endpoint-based caching, while GraphQL …

Why is tree shaking not removing unused code when using ES6 modules in my JavaScript project?

Asked on Wednesday, Jan 07, 2026

Tree shaking is a technique used to eliminate dead code in JavaScript projects, especially when using ES6 modules. If it's not working, there could be several reasons. Here's a basic example and some …

How do I mock a DOM element in Jest for testing event listeners?

Asked on Tuesday, Jan 06, 2026

To mock a DOM element in Jest for testing event listeners, you can use Jest's built-in functions to simulate the DOM environment and attach event listeners to mock elements. // Import necessary functi…