JavaScript 记忆化缓存

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1) Current Task & Steps

Current task: Step 1 - 第一步：实现单参数缓存
实现 memoSquare(n)，重复输入应返回相同结果

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: memoSquare(n)
Self-check: memoSquare(5) => 25
Self-check: memoSquare(3) => 9

2) Beginner Explanation (Current Step)

Step task: 实现 memoSquare(n)，重复输入应返回相同结果
Define function(s): memoSquare, 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 memoSquare(n) {
  return null;
}
// Self-check: memoSquare(5) should return 25
console.log(memoSquare(5));

4) Rule Validation & Hints

📋 当前任务 - Step 1

定义 memoSquare
memoSquare(5)=25
memoSquare(3)=9

🔐 学习提示

📖 快速参考

有副作用的函数不适合直接做记忆化，否则会缓存“错误语义”。

About This Exercise

记忆化（memoization）可以理解成“做题本”：

第一次算出结果时记下来
下次同样输入直接翻记录

适合“纯函数 + 重复输入 + 计算成本高”的场景。

Intermediate⏱ 20-25 min

Learning Objectives

理解缓存 key 与 value 的映射关系
掌握 Map 实现基础缓存逻辑
能输出命中率这种简单缓存指标

Scenario

你在做学习数据计算，用户频繁输入相同参数。为了减少重复计算，你要把结果缓存起来并统计命中效果。

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