之前提到了，最近，孩子的幼兒園讓家長體驗“半日助教活動”，每個家長需要講授15-20分鐘的課程。作為一名程序員，實在沒有能教的課程，只能做了一個小游戲，帶著小朋友們熟悉數字。
在上一章博客中，筆者發布了九宮格中貓捉老鼠的小游戲源碼，下面再把通過bootstrap實現天平效果的源碼發布，供讀者參考。
效果大致是這樣的。通過前端代碼生成一個簡易的天平，天平兩邊分別隨機生成一個數字，點擊較大的數字天平就會傾斜。
天平兩邊生成隨機數的截圖：
點擊較大數字天平傾斜的截圖：
廢話不多說，直接上源碼。
html：
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta http-equiv="X-UA-Compatible" content="ie=edge"><!-- 引入bootstrap --><link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css"> <link rel="stylesheet" href="./css/d2g.css"><title>蹺蹺板比大小</title>
</head>
<body><div id="imgInfo">蹺蹺板比大小</div><!-- 蹺蹺板 --><div class="jenga-container"><div class="jenga-block" id="block1"></div><div class="line" id="line"></div><div class="sjx" id="sjx"></div><div class="jenga-block" id="block2"></div></div>
</body>
<!-- 引入js文件 -->
<script src="./js/d2g.js"></script>
</html>
html代碼沒什么好說的，就是兩個方塊兒，中間用橫線連接，橫線下面再放一個三角形作為支點。
css：
#imgInfo{width: 100%;margin-top: 20px;text-align: center;color: blue;
}
#line {height: 2px; /* 設置為最大高度 */background-color: #000;position: absolute;transform-origin: top; transition: transform 0.8s ease-out;
}
#sjx {width: 100px;height: 100px; /* 設置為最大高度 */background-image: url('../img/sjx1.jpg'); /* 設置背景圖片 */background-size: cover; /* 背景圖片覆蓋整個div區域 */background-position: center; /* 背景圖片居中 */position: absolute;transition: transform 0.8s ease-out;
}
.jenga-container {display: flex;justify-content: space-around;align-items: flex-end;
}.jenga-block {background-color: yellowgreen;margin: 2px 0;text-align: center;transform: translateX(0);transition: transform 0.8s ease-out;
}css中通過transition屬性設置了天平橫線、方塊兒、三角形的傾斜效果。
js：
window.onload = function(xh){// 獲取視口寬度const viewportWidth = window.innerWidth// 獲取視口高度const viewportHeight = window.innerHeightvar imgInfo = document.querySelector('#imgInfo')var line = document.querySelector('#line')var sjx = document.querySelector('#sjx')var block1 = document.querySelector('#block1')var block2 = document.querySelector('#block2')var jengacontainer = document.getElementsByClassName('jenga-container')//為每個容器設置heightfor(var i=0;i<jengacontainer.length;i++){jengacontainer[i].style.height = viewportHeight*0.34+'px'}var jengablock = document.getElementsByClassName('jenga-block')//為每個容器設置heightfor(var i=0;i<jengablock.length;i++){jengablock[i].style.height = viewportHeight*0.24+'px'jengablock[i].style.width = viewportWidth*0.15+'px'jengablock[i].style.fontSize = viewportHeight*0.17+'px'}imgInfo.style.height = viewportHeight*0.12+'px'imgInfo.style.fontSize = viewportHeight*0.06+'px'line.style.width = viewportWidth*0.35+'px'line.style.top = (viewportHeight-viewportHeight*0.63)+'px'sjx.style.top = (viewportHeight-viewportHeight*0.63+2)+'px'sjx.style.width = viewportWidth*0.08+'px'sjx.style.height = viewportWidth*0.08+'px'let szqz1 = Math.floor(Math.random() * 10);block1.innerHTML = szqz1;let szqz2 = getRandomNumber(szqz1)block2.innerHTML = szqz2;/*** 點擊三角形重置數字*/sjx.onclick = function(){var audio1 = new Audio('./audio/py2.MP3');// 播放音頻audio1.play();}/*** 播放音頻*/if(xh!=2){//開始配音var audio = new Audio('./audio/py8.MP3');// 播放音頻audio.play();}/*** block2里面的數字大*/block2.onclick = function(){const y = viewportHeight*0.3block2.style.transform = 'translateY('+y+'px)';//線變斜const y2 = viewportHeight*0.12const radians = Math.atan2(y, viewportWidth*0.35);// 將弧度轉換為角度const degrees = radians * (180 / Math.PI);const a = viewportWidth*0.35const b = viewportHeight*0.3const c= Math.sqrt(a*a + b*b)line.style.width = c+'px';line.style.transform = 'translateY('+y2+'px) rotate('+degrees+'deg)';sjx.style.transform = 'translateY('+(y/2+4)+'px)';//播放音頻var audio = new Audio('./audio/py11.MP3');// 播放音頻audio.play();}/*** block1里面的數字大*/block1.onclick = function(){const y = viewportHeight*0.3block1.style.transform = 'translateY('+y+'px)';//線變斜const y2 = viewportHeight*0.12const radians = Math.atan2(y, viewportWidth*0.35);// 將弧度轉換為角度const degrees = radians * (180 / Math.PI);const a = viewportWidth*0.35const b = viewportHeight*0.3const c= Math.sqrt(a*a + b*b)line.style.width = c+'px';line.style.transform = 'translateY('+y2+'px) rotate('+(-degrees)+'deg)';sjx.style.transform = 'translateY('+(y/2+4)+'px)';//播放音頻var audio = new Audio('./audio/py11.MP3');// 播放音頻audio.play();}
}
function getRandomNumber(exclude) {let num;do {num = Math.floor(Math.random() * 10);} while (num === exclude);return num;
}js中需要注意一下，這里有個小小的算法，因為在數字大的方塊兒下移的時候，中間的天平橫線長度也要跟著變，不然無法連接到兩端。所以，要通過勾股定理計算出天平橫線的長度、傾斜角度和中間三角形下降的距離。在block1/block2.onclick函數中可以看到這個小小的算法。
筆者這里只是實現了很簡單的效果，但大概原理是對的。各位讀者可以自行試試~~~~
