TikTok’s front-end engineer interviews have become increasingly focused on JavaScript execution mechanisms, particularly asynchronous task scheduling, the event loop, microtasks, and macrotasks. Unlike traditional LeetCode-style algorithm questions, these types of assessments dive deep into low-level knowledge and real-world engineering applications. Many candidates may have encountered these concepts in their daily development work, but in a high-pressure interview setting, they often struggle to articulate their understanding clearly, which can cost them the opportunity.

In a recent TikTok front-end engineer interview, one of our clients faced a question that tested their knowledge of the JavaScript event loop. The interviewer shared the code in a collaborative editor and asked the candidate to explain the execution order.

Question:
Explain the execution order of micro / macro task

Question 1:

async function fetchDataFromBackend() {
    return Promise.resolve('data');
}

const func2 = async function() {
    console.log('func2 start');
    console.log('func2 end');
}

const func3 = async function() {
    console.log('func3 start');
    const data = await fetchDataFromBackend();
    console.log('func3 end');
}

When the client first saw the code, they immediately recognized that it was related to JavaScript’s event loop. However, due to nervousness, they found it difficult to organize a structured response. Without CSOAHELP’s real-time interview assistance, their response might have sounded vague and incomplete, such as:

"Uh... this code runs asynchronously, and func3 has an await, so it should wait for the Promise to resolve? Then maybe the synchronous code runs first?"

This kind of response is neither precise nor well-structured. The interviewer might follow up with a question like: “Why does async/await create a microtask? How is it scheduled in the event loop?” If a candidate’s thoughts are already scrambled, it becomes difficult to continue with a well-reasoned explanation.

CSOAHELP provided real-time textual assistance throughout the interview, ensuring that the client could express their understanding with clarity and precision at critical moments. For this question, we provided a complete answer template:

"JavaScript is single-threaded, and its execution follows a sequence of synchronous tasks, microtasks, and macrotasks. The first step is to execute all synchronous tasks. When func2() is called, it logs func2 start, then func2 end. Next, when func3() is called, it logs func3 start. The execution reaches await fetchDataFromBackend(), which calls Promise.resolve('data'), creating a microtask and pausing func3() while waiting for the Promise to resolve. Since JavaScript follows an event loop mechanism, once all synchronous tasks are completed, the event loop checks the microtask queue. At this point, the resolved microtask executes, logging func3 end.”

This answer provides a clear explanation of the execution order while incorporating the concept of microtask scheduling and how async/await affects execution.

The interviewer then followed up with: “What would happen if fetchDataFromBackend() used setTimeout() instead of Promise.resolve()?” Since CSOAHELP had already prepared the client for such a follow-up, they quickly responded:

"If fetchDataFromBackend() used setTimeout() instead of Promise.resolve(), it would be placed in the macrotask queue. Since macrotasks have a lower execution priority than microtasks, it would only run after all synchronous tasks and microtasks have completed execution.”

The interviewer nodded approvingly, satisfied with the response. This interview was a success because the client not only understood JavaScript’s event loop but, more importantly, CSOAHELP’s structured answer guidance helped them articulate their knowledge logically and confidently, avoiding confusion due to nervousness.

Many job seekers face similar challenges in interviews. Even with thorough preparation, the pressure of a real interview can cause candidates to blank out or struggle with articulation. CSOAHELP’s real-time interview assistance is designed precisely for these situations. We provide full answer templates, not just keyword hints, ensuring that candidates can simply follow along and present a complete, structured response without missing key details. Beyond correctness, we help candidates frame their explanations in a way that interviewers appreciate, making their answers clear, concise, and compelling.

In addition to structured answers, we also anticipate potential follow-up questions from interviewers, helping candidates build a more comprehensive understanding of the topic so they can respond confidently to any additional inquiries. Thanks to this approach, our client showcased both technical proficiency and strong communication skills in the TikTok interview, successfully passing the technical round.

If you’re preparing for interviews at TikTok, Google, Meta, Amazon, or other top tech companies, and you don’t want nerves or unclear explanations to cost you an opportunity, CSOAHELP’s real-time interview assistance is the perfect solution. We don’t just reinforce your technical knowledge—we ensure that you perform at your absolute best in high-stakes moments, making your interview responses stand out from the competition.

经过csoahelp的面试辅助，候选人获取了良好的面试表现。如果您需要面试辅助或面试代面服务，帮助您进入梦想中的大厂，请随时联系我。

If you need more interview support or interview proxy practice, feel free to contact us. We offer comprehensive interview support services to help you successfully land a job at your dream company.