javascript-development-lab/04-function/index.html at main · coowinit/javascript-development-lab · GitHub

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<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>04 Function｜JavaScript Development Lab</title>
  <link rel="stylesheet" href="css/style.css">
</head>
<body>
  <main class="container">
    <header class="hero">
      <p class="eyebrow">JavaScript Development Lab · 04</p>
      <h1>函数、参数与返回值</h1>
      <p class="lead">通过一个最小价格计算场景，观察函数如何接收数据、执行一段可复用逻辑，再通过 <code>return</code> 把结果交回程序。</p>
    </header>

    <section class="panel">
      <div class="section-head">
        <div>
          <span class="step">实验 A</span>
          <h2>普通函数：计算小计</h2>
        </div>
        <code>calculateSubtotal(price, quantity)</code>
      </div>
      <div class="result-grid">
        <div class="result-item"><span>单价</span><strong id="unit-price">-</strong></div>
        <div class="result-item"><span>数量</span><strong id="quantity">-</strong></div>
        <div class="result-item primary"><span>小计</span><strong id="subtotal">-</strong></div>
      </div>
    </section>

    <section class="panel">
      <div class="section-head">
        <div>
          <span class="step">实验 B</span>
          <h2>参数 + return：计算折后价</h2>
        </div>
        <code>applyDiscount(amount, discount)</code>
      </div>
      <div class="result-grid">
        <div class="result-item"><span>原始金额</span><strong id="original-total">-</strong></div>
        <div class="result-item"><span>折扣</span><strong id="discount-rate">-</strong></div>
        <div class="result-item primary"><span>折后金额</span><strong id="discounted-total">-</strong></div>
      </div>
    </section>

    <section class="panel">
      <div class="section-head">
        <div>
          <span class="step">实验 C</span>
          <h2>箭头函数：格式化价格</h2>
        </div>
        <code>const formatPrice = value =&gt; ...</code>
      </div>
      <p class="demo-text">格式化后的价格：<strong id="formatted-price">-</strong></p>
    </section>

    <section class="panel note">
      <h2>本章观察重点</h2>
      <ol>
        <li>函数把重复逻辑放到一个有名字的代码块中。</li>
        <li>参数是函数接收的数据，调用函数时传入的具体值称为实参。</li>
        <li><code>return</code> 会把函数内部计算结果返回给调用位置。</li>
        <li>函数内部声明的变量通常只在函数内部有效，这就是作用域的基础。</li>
        <li>箭头函数是现代 JavaScript 中常见的函数写法，但本质仍然是在封装逻辑。</li>
      </ol>
    </section>
  </main>

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