JavaScript 防抖与节流

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1) Current Task & Steps

Current task: Step 1 - 第一步：防抖语义模拟
实现 debounceCount(calls)，只返回最后一次触发计数（即 1）

Write your code in `script.js` for the current Step.
Click "Run Validation" to check if rules pass.
Once current Step passes, the next step unlocks automatically.
You need to pass Step 1 first to unlock Step 2.

Step Deliverables (Check these)

Define function: debounceCount(calls)
Self-check: debounceCount(10) => 1
Self-check: debounceCount(1) => 1

2) Beginner Explanation (Current Step)

Step task: 实现 debounceCount(calls)，只返回最后一次触发计数（即 1）
Define function(s): debounceCount, then verify results with test inputs.
This step has a specific expected result. Focus on making the function return the correct value.
A function is a reusable block of code. Define it first, then call it.
`return` sends a result back. Without return, you usually can't get the function's result.

3) Starter Template (Type along)

function debounceCount(calls) {
  return null;
}
// Self-check: debounceCount(10) should return 1
console.log(debounceCount(10));

4) Rule Validation & Hints

📋 当前任务 - Step 1

定义 debounceCount
debounceCount(10)=1
debounceCount(1)=1

🔐 学习提示

📖 快速参考

不要把“防抖/节流”当成固定模板题，先判断业务想保留“最后一次”还是“固定频率”。

About This Exercise

防抖和节流不是复杂算法，核心都是“控制触发频率”。

防抖：连续触发时只要最后一次（常见于搜索输入）
节流：固定时间窗口内最多触发一次（常见于滚动、拖拽）

Intermediate⏱ 25-30 min

Learning Objectives

理解防抖与节流的行为差异
能用简单函数表达两种策略结果
能根据场景做正确策略选择

Scenario

你在做课程搜索和滚动列表：搜索框不想每个字都请求接口，滚动事件也不能毫无节制地触发。

Why Do This

Frontend JS is not just about knowing the syntax — the key is reliably manipulating the DOM and managing interaction state.
Break down the event flow (trigger -> handle -> update UI) before coding, and you will make significantly fewer errors.
Rule-based validation helps you develop a testable frontend mindset.

Hands-on Practice

Write out the event flow in comments first, then implement the functions.
Add an edge case branch for invalid input or empty data.
Explain why each validation rule is needed.

Common Mistakes

Only testing the happy path without verifying edge inputs or repeated clicks.
Mixing event binding and state updates together, making future maintenance difficult.
Console output looks correct but the UI is not actually updated.

Deliverable

A reusable interaction component scaffold (event flow description + key functions + edge case handling).

My Progress

Completed Steps0 / 3

Total Attempts0

Best Score0%

Completion Criteria (Checkable)

Confirm before completing this Lab

All rules for the current step passCan explain each line of your codeCan name a real-world business scenario for this

Reflection Questions (Recommended)

Describe the event flow of this Lab in 2-3 sentences (trigger -> handle -> update).

What edge case did you add? Why is it easy to miss?

How confident are you with this interaction pattern now?

Not confident yet, need more practiceCan complete similar tasks independentlyCan teach others how to do it