# JavaScript實作DAY5

2024 iThome 鐵人賽

DAY 28

JavaScript

解鎖第一個人生成就清單：Javascript鐵人學習系列第 28 篇

16th鐵人賽

s1411132022

團隊NUTC_IMAC

2024-10-07 18:54:40

73 瀏覽

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Mouse Shandow

讓畫面可以用滑鼠左右橫移

完成圖:

HTML
定義一個包含25個子元素的div，每個div代表一個數字

<!DOCTYPE html>
<html lang="zh-TW">
<head>
  <meta charset="UTF-8">
  <title>Click and Drag</title>
  <link rel="stylesheet" href="style.css">
</head>
<body>
  <div class="items">
    <div class="item item1">01</div>
    <div class="item item2">02</div>
    <div class="item item3">03</div>
    <div class="item item4">04</div>
    <div class="item item5">05</div>
    <div class="item item6">06</div>
    <div class="item item7">07</div>
    <div class="item item8">08</div>
    <div class="item item9">09</div>
    <div class="item item10">10</div>
    <div class="item item11">11</div>
    <div class="item item12">12</div>
    <div class="item item13">13</div>
    <div class="item item14">14</div>
    <div class="item item15">15</div>
    <div class="item item16">16</div>
    <div class="item item17">17</div>
    <div class="item item18">18</div>
    <div class="item item19">19</div>
    <div class="item item20">20</div>
    <div class="item item21">21</div>
    <div class="item item22">22</div>
    <div class="item item23">23</div>
    <div class="item item24">24</div>
    <div class="item item25">25</div>
  </div>

CSS

<style>
html {
  box-sizing: border-box;
  background: url('https://source.unsplash.com/NFs6dRTBgaM/2000x2000') fixed;
  background-size: cover;
}

*, *:before, *:after {
  box-sizing: inherit;
}

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: sans-serif;
  font-size: 20px;
  margin: 0;
}

.items {
  height:800px;
  padding: 100px;
  width:100%;
  border:1px solid white;
  overflow-x: scroll;
  overflow-y: hidden;
  white-space: nowrap;
  user-select: none;
  cursor: pointer;
  transition: all 0.2s;
  transform: scale(0.98);
  will-change: transform;
  position: relative;
  background: rgba(255,255,255,0.1);
  font-size: 0;
  perspective: 500px;
}

.items.active {
  background: rgba(255,255,255,0.3);
  cursor: grabbing;
  cursor: -webkit-grabbing;
  transform: scale(1);
}

.item {
  width:200px;
  height: calc(100% - 40px);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 80px;
  font-weight: 100;
  color:rgba(0,0,0,0.15);
  box-shadow: inset 0 0 0 10px rgba(0,0,0,0.15);
}

.item:nth-child(9n+1) { background: dodgerblue;}
.item:nth-child(9n+2) { background: goldenrod;}
.item:nth-child(9n+3) { background: paleturquoise;}
.item:nth-child(9n+4) { background: gold;}
.item:nth-child(9n+5) { background: cadetblue;}
.item:nth-child(9n+6) { background: tomato;}
.item:nth-child(9n+7) { background: lightcoral;}
.item:nth-child(9n+8) { background: darkslateblue;}
.item:nth-child(9n+9) { background: rebeccapurple;}

.item:nth-child(even) { transform: scaleX(1.31) rotateY(40deg); }
.item:nth-child(odd) { transform: scaleX(1.31) rotateY(-40deg); }
</style>

Javascript
選取 .items 元素並設置一些初始變數。
當滑鼠按下時，記錄滑鼠按下的位置和當前的滾動位置，並設置滑鼠按下狀態。
當滑鼠移出或釋放時，重置滑鼠按下狀態並移除 active 類。
當滑鼠移動時，如果滑鼠處於按下狀態，計算新的滾動位置並更新 scrollLeft 屬性，使元素隨著滑鼠的移動而滾動。

<script>
  const slider = document.querySelector('.items');
  let isDown = false;
  let startX;
  let scrollLeft;

  slider.addEventListener('mousedown', (e) => {
    isDown = true;
    slider.classList.add('active');
    startX = e.pageX - slider.offsetLeft;
    scrollLeft = slider.scrollLeft;
  });

  slider.addEventListener('mouseleave', () => {
    isDown = false;
    slider.classList.remove('active');
  });

  slider.addEventListener('mouseup', () => {
    isDown = false;
    slider.classList.remove('active');
  });

  slider.addEventListener('mousemove', (e) => {
    if (!isDown) return;  // stop the fn from running
    e.preventDefault();
    const x = e.pageX - slider.offsetLeft;
    const walk = (x - startX) * 3;
    slider.scrollLeft = scrollLeft - walk;
  });

</script>