Answer
Synchronous: Executes line-by-line and blocks.
Asynchronous: Non-blocking; uses callbacks, promises, async/await.
Quick Answer
Synchronous: each operation runs in order, one at a time — the next line waits for the current one to finish. Asynchronous: an operation starts and the code continues without waiting — when the operation completes, a callback or Promise resolves. JavaScript is single-threaded, so async is essential for I/O (network, file) without blocking the main thread.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ