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In JavaScript, what is the difference between synchronous and asynchronous code?

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In JavaScript, what is the difference between synchronous and asynchronous code?

Asked on Jul 01, 2025

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Synchronous code in JavaScript runs sequentially, blocking the execution of subsequent code until the current operation completes, while asynchronous code allows other operations to run before the current one completes, enabling non-blocking behavior.

<!-- BEGIN COPY / PASTE -->
        // Synchronous example
        console.log("Start");
        console.log("Middle");
        console.log("End");

        // Asynchronous example
        console.log("Start");
        setTimeout(() => {
            console.log("Middle");
        }, 1000);
        console.log("End");
        <!-- END COPY / PASTE -->

Additional Comment:

In the synchronous example, "Start", "Middle", and "End" are logged in order.
In the asynchronous example, "Start" and "End" are logged first, and "Middle" is logged after a 1-second delay due to the setTimeout function.
Asynchronous code is useful for operations that take time, such as network requests, without freezing the UI or blocking other operations.

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In JavaScript, what is the difference between synchronous and asynchronous code?

Asked on Jul 01, 2025

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