JavaScript Interview Question #199

What JavaScript topics should a senior developer understand for debugging production issues?

Advanced JavaScript, Practical Problems & Senior Interview Scenarios Senior Advanced

Quick Interview Answer

A senior developer should understand scope and closures, this binding, prototypes, asynchronous execution, Promise error propagation, the event loop, browser rendering, memory reachability, network behavior, DOM events, security boundaries, modules, and build output.

Detailed Explanation

Debugging should be evidence-driven. Use stack traces, source maps, browser developer tools, network traces, performance profiles, heap snapshots, structured logs, monitoring, and reproducible inputs. The developer should separate symptoms from root causes and verify that a proposed fix does not introduce regressions.

Code Example

async function loadFeature() {
    performance.mark("feature-start");

    try {
        return await fetchFeature();
    } catch (error) {
        console.error("Feature failed", {
            name: error.name,
            message: error.message,
            stack: error.stack
        });

        throw error;
    } finally {
        performance.mark("feature-end");
        performance.measure(
            "feature",
            "feature-start",
            "feature-end"
        );
    }
}