JavaScript 运算符

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1) Current Task & Steps

Current task: Step 1 - 算术运算
定义一个 calculate 函数，计算两个数的和、差、积、商，返回一个对象。

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: calculate(first, second)
Self-check: calculate(10, 3) => {"sum":13,"diff":7,"product":30,"quotient":3.3333333333333335}

2) Beginner Explanation (Current Step)

Step task: 定义一个 calculate 函数，计算两个数的和、差、积、商，返回一个对象。
Define function(s): calculate, 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 calculate(first, second) {
  return null;
}
// Self-check: calculate(10, 3) should return {"sum":13,"diff":7,"product":30,"quotient":3.3333333333333335}
console.log(calculate(10, 3));

4) Rule Validation & Hints

📋 当前任务 - Step 1

定义 calculate 函数
返回正确的计算结果

💡 步骤提示

🔐 学习提示

📖 快速参考

始终使用 === 进行比较。== 会进行类型转换，可能导致意外结果。

About This Exercise

运算符可以理解为“数据之间怎么计算、怎么比较”的规则。

这一关按“算术 -> 比较 -> 逻辑”顺序走，先会算，再会判断。

你将学到：

算术运算符：+、-、*、/、%
比较运算符：===、!==、>、<
逻辑运算符：&&、||、!
空值合并：??

Beginner⏱ 15-20 min

Learning Objectives

掌握基本算术运算
理解比较运算符的区别
学会使用逻辑运算符
了解空值合并运算符

Scenario

你在做一个小工具：先算价格，再判断是否相等，最后判断一个人是否满足条件。这是新手最常见的真实编程流程。

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